Interactions on record — worth a quick check against your medications. Check your meds →
Dietary supplement

T.-W Ingredients & Drug Interactions

by Pure Herbs

T.-W label
See full label image
Capsule Category: Other Combinations
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 30, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking T.-W against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

T.-W is a dietary supplement by Pure Herbs with 4 active ingredients. Its ingredients are commonly taken for source of iodine and minerals, thyroid support, respiratory issues and cough.Based on those ingredients, 1,128 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Bladderwrack, wild Lettuce 4:1 extract powder, Dulse. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against T.-W by Pure Herbs

Ask about any prescription or over-the-counter medication and we check it for interactions with T.-W by Pure Herbs — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of T.-W by Pure Herbs

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Oct 6, 2026

What’s inside

Low disclosure
Ingredient Transparency · database check
Low

Most active ingredients don't disclose an individual amount — you can't tell how much of each you're getting.

Why this rating?
  • The label discloses an exact amount for 0 of its 4 active ingredients.
  • “Proprietary Blend” is a proprietary blend — the label gives one combined amount (700 mg) without saying how much of each component you get.

Pure Herbs T.-W is a four-ingredient capsule blend. Irish Moss (also called Sea Moss) is a seaweed rich in iodine and minerals.

Wild Lettuce 4:1 extract powder is a concentrated form of wild lettuce leaf, traditionally used for its relaxing properties. Dulse is a red seaweed high in both iodine and potassium.

Bladderwrack (Fucus vesiculosus) is a brown seaweed also high in iodine. The capsule itself contains gelatin as an inactive ingredient.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: support healthy thyroid function.
  • We looked for evidence on: Hypothyroidism, Iodine deficiency, Thyroid health, Thyroid hormone metabolism.
  • The closest evidence on file: Fucus Vesiculosus is rated "Insufficient Reliable Evidence To Rate" for Hypothyroidism (Natural Medicines).
  • Also on file: Fucus Vesiculosus is rated "Insufficient Reliable Evidence To Rate" for Iodine deficiency.
  • Also on file: Dulse is rated "Insufficient Reliable Evidence To Rate" for Iodine deficiency.

The evidence supporting these ingredients is limited. Irish Moss has been studied for fatigue, muscle strength, chronic pain, and quality of life, but the data we hold rates all of these as insufficient to draw firm conclusions.

Dulse has been looked at for cholesterol and iodine deficiency without conclusive results. Bladderwrack's effectiveness for aging skin, heart disease, constipation, diarrhea, and indigestion is also rated insufficient.

Wild Lettuce carries no effectiveness ratings in our data. In short, the ingredients in this product lack established evidence for their intended uses.

The evidence, ingredient by ingredient Sea Moss Wild Lettuce Dulse Fucus Vesiculosus

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 3 of the 4 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 4 of 4.
  • General safety write-ups exist for 4 of 4.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Irish Moss and Bladderwrack are generally viewed as foods, but their iodine and heavy-metal content can vary unpredictably in supplements and warrant caution. During pregnancy, Irish Moss should be avoided due to variable iodine levels and possible contaminants; Bladderwrack is rated possibly unsafe in pregnancy because excess iodine and potential heavy metals pose a risk.

While breastfeeding, both should be avoided—iodine passes into breast milk and may affect your baby's thyroid. Wild Lettuce has limited safety data; it should be avoided in pregnancy and while breastfeeding.

Dulse is generally safe as food but concentrated supplements contain high potassium and unpredictable iodine, so avoid supplement doses during pregnancy and breastfeeding unless you've checked with your doctor. Orally, Irish Moss has been linked to constipation and diarrhea in one study.

Properly harvested, mature Wild Lettuce appears well tolerated in normal amounts, but large doses or prematurely harvested plant can cause dizziness, headache, sweating, rapid heartbeat, dilated pupils, ringing in the ears, vision problems, drowsiness, and in rare cases respiratory depression or coma. Bladderwrack's high iodine can cause goiter, too much or too little thyroid activity, and in rare cases thyroid cancer.

Side effects, ingredient by ingredient Sea Moss Wild Lettuce Dulse Fucus Vesiculosus

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 4 of the 4 matched ingredients can interact with medications — Wild Lettuce, Fucus Vesiculosus, Dulse, Sea Moss.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; heart-rhythm medications; lithium.
  • For scale: 1,129 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Check before taking this product if you use thyroid hormone, antithyroid drugs, amiodarone (a heart rhythm medication), lithium, digoxin (a heart medication), potassium-sparing diuretics, ACE inhibitors, ARBs, blood thinners or antiplatelet drugs, central nervous system depressants (sedatives, sleep aids, opioids), or medications broken down by your liver through CYP2D6, CYP2C9, or CYP3A4 pathways. The iodine in three of the four ingredients poses the greatest risk; potassium, sedative effects, and theoretical liver-enzyme interactions are secondary concerns.

Ask your doctor or pharmacist to check your exact medications against this product.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFormula with limited ingredient disclosure with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

This product is built on seaweeds and an herbal extract with limited effectiveness evidence and significant iodine and potassium content. If you have a thyroid condition, take heart or blood pressure medication, use lithium, or take a blood thinner, you'll need to clear this with your doctor or pharmacist before starting—the risks outweigh any unproven benefit.

Even if you don't take those medications, talk it over with your own healthcare provider, especially if you're pregnant, breastfeeding, or planning to be.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 4 of 4 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Apr 25, 2017.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about T.-W, straight from the product label.

Brand Pure Herbs
Net contents 100 Capsule(s)
Market status On market
Date entered into DSLD Apr 25, 2017
DSLD ID 73037
Product type Other Combinations
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Organic, Gluten Free, Dairy Free, Sugar Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for T.-W by Pure Herbs, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
100
IngredientAmount% DV
Proprietary Blend700 mg--
Irish Moss0 NP--
wild Lettuce 4:1 extract powder0 NP--
Dulse0 NP--
Bladderwrack0 NP--

Other ingredients: Gelatin

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
General Statements

T.-W (Thyroid) No expense has been spared to provide the finest nature has to offer.

Description: T.-W - (liquid or capsules) to support healthy thyroid function.

Historical Uses

The thyroid is a large gland with the appearance of a bunch of flattened grapes, which sets at the base of the neck under the voice box. Here is the sub-station in control of blood calcium levels and calm nerves, strong nails, weight control, energy, hair that does not break off and healthy skin. When the thyroid is properly nourished, hands and feet warm up and fibroid tumors are prevented and/or reabsorbed. Remember, not just the thyroid requires a high-grade natural source of iodine; the ovaries store iodine also for their proper health. The thyroid, however, is a "hog" and takes its iodine first. If there is not enough for both, or either, the thyroid takes it all and thus, fibroid tumors occur. If the thyroid does not get enough nutrients it may swell in size in an attempt to absorb more by getting bigger. The base of the neck may become fat and or the thyroid may enlarge internally. This is a common cause of feeling like there is always something in the throat that cannot be swallowed. If the chemical iodine added to salt actually worked, with all the salt in the typical diet, there would be no problems as listed here. White salt is refined salt, which is another way of saying it has been robbed of every thing except sodium and chlorine and chemical iodine, which may be added to it. If a person has a "taste" for salt, then assume they are mineral deficient and lacking the assortment of the many true mineral salts, which should be in the body and would be found in unrefined salt. Much better than unrefined salt, would be to take the mineral salts from the living lattice of sea vegetables which have them organized in a form to support life. With that in mind, we take V.M.-W (Vital Minerals), T.-W or A.C.S. (All Cells "Salts" minerals) for a balanced mineral profile. Most so-called "weight loss diets" do not result in weight loss because they do not address proper thyroid nutrition and thus regulate the speed at which food is burned and energy is released. You may also find, with proper thyroid nutrition, the fingers no longer shake when the arms and hands are extended and the fingers spread apart; as well as strange fears that simply disappear.

Note: One capsule equals about 20 drops of the liquid.

All Pure Herbs products are independently lab tested 3 times for accuracy and purity in accordance with FDA regulations. Pure Herbs, LTD. Making fine herbal extracts since 1976 See specials

The information above is provided by The Center for Building Better Health Naturally, inc.

FDA Statement of Identity

Herbal Supplement

General

Code: TWC

Formula

(Dulse, bladderwrack, wild lettuce, irish moss).

Combination: dulse, bladderwrack, wild lettuce, irish moss.

Formulation

T.-W (Thyroid) - Approx. 700 mg 100 capsules organic, natural iodine and more for the thyroid.

Contains no sugar, salt, starch, yeast, wheat, gluten, corn, milk, egg, shellfish or preservatives.

Suggested/Recommended/Usage/Directions

Capsule Directions: As an herbal supplement, take one capsule daily or as directed by your healthcare practitioner.

FDA Disclaimer Statement

This product has not been evaluated by the US Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

This information is about historical observations and historical information relating to herbs. This information is not intended to be a substitute for medical advice by licensed physicians. A person should consult a physician regularly in all matters relating to medical problems, especially in matters of diagnosing, treating or curing diseases or other physical or mental conditions. This information has not been verified by the American Medical Association or the Food and Drug Administration Disclaimer Policy The products and the claims made about specific products on or through this site have not been evaluated by Heaven & Herbs or the United States Food and Drug Administration and are not approved to diagnose, treat, cure or prevent disease. The information provided on this site is for informational purposes only and is not intended as a substitute for advice from your physician or other health care professional or any information contained on or in any product label or packaging. You should not use the information on this site for diagnosis or treatment of any health problem or for prescription of any medication or other treatment. You should consult with a healthcare professional before starting any diet, exercise or supplementation program, before taking any medication, or if you have or suspect you might have a health problem. By ordering products from heavenandherbs.com, you submit that you are in agreement with our disclaimer and terms of use.

Precautions

You should consult with a healthcare professional before starting any diet, exercise or supplementation program, before taking any medication, or if you have or suspect you might have a health problem.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

T.-W by Pure Herbs label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

T.-W label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in T.-W by Pure Herbs

These are the 4 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Servings per container100 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Proprietary Blend

700 mg per serving

Other (inactive) ingredients: Gelatin. These complete the product’s ingredient list but are not active constituents.

Interaction report

T.-W by Pure Herbs Drug Interactions

Want to check YOUR meds against T.-W?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
1,128Drugs
416 Moderate 712 Minor

Ingredients driving the most interactions

Bladderwrack 893
wild Lettuce 4:1 extract powder 393
Dulse 85
Irish Moss 22

Individual Drug Interactions

The ingredients in T.-W interact with 1,128 drugs. Click any drug to see the details.

4 of the 4 ingredients in T.-W interact with drugs. Each result below shows which ingredient is responsible. Bladderwrack wild Lettuce 4:1 extract powder Dulse Irish Moss

Each ingredient & the kinds of drugs it affects

For each ingredient in T.-W with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

Bladderwrack9 drug types · 893 drugs

Amiodarone (Cordarone)

Theoretically, combining Fucus vesiculosus with amiodarone might cause excessively high iodine levels.
Fucus vesiculosus contains high concentrations of iodine. Amiodarone contains 37.3% iodine and can increase iodine levels. Concomitant use might increase the risk of having excessive iodine levels and adversely affecting thyroid function. Monitor thyroid function.

Likelihood Probable Evidence D
Antithyroid Drugs

Due to its iodine content, Fucus vesiculosus might alter the effects of antithyroid drugs.
Fucus vesiculosus contains high concentrations of iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking Fucus vesiculosus while using antithyroid drugs could alter the effects of the antithyroid drugs.

Likelihood Possible Evidence D
Lithium

Concomitant use of Fucus vesiculosus and lithium has resulted in hyperthyroidism.
There is a case of hyperthyroidism occurring in a patient taking Fucus vesiculosus and lithium. Monitor thyroid hormones closely in patients taking lithium and Fucus vesiculosus concomitantly.

Likelihood Possible Evidence D
Thyroid Hormone

Due to its iodine content, Fucus vesiculosus might alter the effects of thyroid hormone.
Fucus vesiculosus contains high concentrations of iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking Fucus vesiculosus while using thyroid hormone could alter the effects of thyroid hormone.

Likelihood Possible Evidence D
Anticoagulant/Antiplatelet Drugs

Theoretically, taking Fucus vesiculosus with antiplatelet or anticoagulant drugs might increase the risk of bruising and bleeding.
In vitro evidence suggests that a constituent of Fucus vesiculosus, known as fucoidan, has anticoagulant effects. However, in clinical research, fucoidan does not seem to have significant anticoagulant activity when taken orally, possibly due to poor absorption.

Likelihood Unlikely Evidence D
Cytochrome P450 2C8 (Cyp2C8) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP2C8 substrates might increase the risk for adverse effects.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, inhibits CYP2C8. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP2C9 substrates might increase the risk for adverse effects.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, inhibits CYP2C9. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2D6 (Cyp2D6) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP2D6 substrates might alter the effects of these substrates.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, both inhibits and induces CYP2D6. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, concomitant use of Fucus vesiculosus with CYP3A4 substrates might increase the risk for adverse effects.
In vitro research shows that fucoidan, a constituent of Fucus vesiculosus, inhibits CYP3A4. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Bladderwrack full monograph & interactions

wild Lettuce 4:1 extract powder2 drug types · 393 drugs

Anticholinergic Drugs

Studies report varying evidence on whether or not wild lettuce contains hyoscyamine, an anticholinergic drug. If it does, it appears to be in very low amounts. Nevertheless, there have been case reports of individuals consuming large amounts of wild lettuce experiencing anticholinergic-related side effects, such as constipation, dry mouth, dizziness, and sweating. Therefore, if you are already taking a drug with anticholinergic effects, you should be cautious about combining it with wild lettuce as the risk of side effects may be increased.

Likelihood Possible Evidence D
Cns Depressants

Theoretically, concomitant use with drugs with sedative effects might cause additive therapeutic effects and adverse effects.

Likelihood Possible Evidence D
wild Lettuce 4:1 extract powder full monograph & interactions

Dulse7 drug types · 85 drugs

Amiodarine (Cordarone)

Theoretically, combining dulse with amiodarone might cause excessively high iodine levels.
Dulse is rich in iodine, and amiodarone contains 37.3% iodine and can increase iodine levels.

Likelihood Possible Evidence D
Antithyroid Drugs

Theoretically, due to its iodine content, dulse might alter the effects of antithyroid drugs.
Dulse is rich in iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history.

Likelihood Possible Evidence D
Digoxin (Lanoxin)

Theoretically, dulse might increase the risk of hyperkalemia when taken with digoxin.
Dulse is rich in potassium, and digoxin can increase potassium levels in the blood. This interaction has not been demonstrated in humans.

Likelihood Possible Evidence D
Thyroid Hormone

Theoretically, due to its iodine content, dulse might alter the effects of thyroid hormone.
Dulse is rich in iodine. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Although dulse has been associated with a statistically significant increase in thyroid stimulating hormone (TSH) levels in clinical research, clinically significant increases have not been documented.

Likelihood Possible Evidence D
Ace Inhibitors (Aceis)

Theoretically, dulse might increase the risk of hyperkalemia when taken with ACEIs.
Dulse is rich in potassium. ACEIs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion. Concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels. However, using these drugs while consuming dulse in quantities that provide larger amounts of potassium daily might increase the risk of hyperkalemia. Additionally, in vitro research suggests that dulse protein hydrolysates inhibit the activity of ACE. However, these effects have not been demonstrated in humans.

Likelihood Possible Evidence D
Angiotensin Receptor Blockers (Arbs)

Theoretically, dulse might increase the risk of hyperkalemia when taken with ARBs.
Dulse is rich in potassium. ARBs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion. Concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels. However, using these drugs while consuming dulse in quantities that provide higher amounts of potassium daily might increase the risk of hyperkalemia. Additionally, in vitro research suggests that dulse protein hydrolysates inhibit the activity of angiotensin converting enzyme (ACE). However, these effects have not been demonstrated in humans.

Likelihood Possible Evidence D
Potassium-Sparing Diuretics

Theoretically, dulse might increase the risk of hyperkalemia when taken with potassium-sparing diuretics.
Dulse is rich in potassium, and potassium-sparing diuretics can increase potassium levels in the blood. This interaction has not been shown in humans.

Likelihood Possible Evidence D
Dulse full monograph & interactions

Irish Moss3 drug types · 22 drugs

Amiodarone (Cordarone)

Theoretically, combining sea moss with amiodarone might cause excessively high iodine levels.
Amiodarone contains 37.3% iodine and can increase iodine levels. Concomitant use with sea moss, which contains approximately 4-7 mcg of iodine per gram, might increase the risk of adverse effects from iodine, including altered thyroid function.

Likelihood Possible Evidence D
Antithyroid Drugs

Due to its iodine content, sea moss might alter the effects of antithyroid drugs.
Sea moss contains approximately 4-7 mcg of iodine per gram. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking sea moss could theoretically alter the effects of antithyroid drugs.

Likelihood Possible Evidence D
Thyroid Hormone

Due to its iodine content, sea moss might alter the effects of thyroid hormone.
Sea moss contains approximately 4-7 mcg of iodine per gram. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking sea moss could theoretically alter the effects of thyroid hormone.

Likelihood Possible Evidence D
Irish Moss full monograph & interactions
The maker

Brand information

Manufacturer and brand details for T.-W, from the product label.

Pure Herbs

See all Pure Herbs products
Name
Pure Herbs, LTD.
Pharmacist Counseling Corner

T.-W by Pure Herbs: Common Questions

Does T.-W by Pure Herbs interact with any medications?
Yes. Based on its ingredients, T.-W has a known interaction with 1,128 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
T.-W contains 4 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take this while I'm pregnant?
No, not safely based on the data we have. Irish Moss and Bladderwrack should be avoided during pregnancy because iodine and heavy-metal levels are unpredictable, and Bladderwrack is rated possibly unsafe. Wild Lettuce also lacks enough safety information to recommend it in pregnancy. Talk with your doctor or pharmacist before taking any supplement while pregnant.
Is it safe to take while breastfeeding?
No. Irish Moss, Bladderwrack, and Wild Lettuce should all be avoided while breastfeeding—iodine passes into breast milk and may affect your baby's thyroid, and the safety data is too limited for the others. Check with your doctor or pharmacist if you're considering it.
What is Wild Lettuce supposed to do?
Wild Lettuce is traditionally used for its relaxing or sedative effects, but our data holds no effectiveness ratings for it—meaning the evidence hasn't been established. In large amounts, especially if prematurely harvested, it can cause dizziness, headache, drowsiness, and in rare cases more serious effects.
Can this product help with my thyroid condition?
No. Irish Moss, Dulse, and Bladderwrack all contain iodine, and high iodine can actually disrupt thyroid function—whether you have too much or too little thyroid activity. If you have a thyroid condition or take thyroid medication, do not take this product without talking to your doctor first.
What are the most common side effects?
Irish Moss has been reported to cause constipation or diarrhea. Wild Lettuce, taken in normal amounts of mature plant, is generally well tolerated, but large doses can cause dizziness, headache, rapid heartbeat, and drowsiness. Bladderwrack's high iodine may cause goiter or thyroid dysfunction. Dulse itself has no reported adverse effects in the data we hold.
Should I be worried about heavy metals?
Yes, it's a real concern. Irish Moss, Dulse, and Bladderwrack are seaweeds that can absorb heavy metals from ocean water, and contaminant levels vary unpredictably in supplements. This is especially important to avoid during pregnancy and breastfeeding, but caution applies generally.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

T.-W label
Go deeper

The Full Monographs Behind T.-W’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Sea Moss

Interacts with 22 drugs

Sea moss is a type of red seaweed that is naturally rich in iodine and several minerals, and it is popular as a 'whole-food' supplement. Strong human evidence for most of its health claims i...

Read the full Sea Moss monograph → Herb & supplement monograph

Wild Lettuce

Interacts with 393 drugs

Wild lettuce is a traditional herb used mainly for sleep, anxiety, and pain, but solid human research supporting these uses is very limited. Because its safety is not well studied, it should...

Read the full Wild Lettuce monograph → Herb & supplement monograph

Dulse

Interacts with 85 drugs

Dulse is a red seaweed eaten as a food in many coastal cultures and is a natural source of iodine, potassium, protein, and antioxidant compounds. As a food it is generally considered safe fo...

Read the full Dulse monograph → Herb & supplement monograph

Fucus Vesiculosus

Interacts with 893 drugs

Fucus vesiculosus (bladderwrack) is a brown seaweed rich in iodine that has been used traditionally for thyroid concerns, weight, and skin. There is little solid human evidence to support mo...

Read the full Fucus Vesiculosus monograph →
Sources

Sources & How We Checked

T.-W's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 28 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Sea Moss 3 references
  1. Darias-Rosales J, Rubio C, Gutiérrez ÁJ, Paz S, Hardisson A. Risk assessment of iodine intake from the consumption of red seaweeds (Palmaria palmata and Chondrus crispus). Environ Sci Pollut Res Int 2020;27(36):45737-45741. PubMed
  2. U.S. Department of Agriculture (USDA). Agricultural Research Service. FoodData Central. Seaweed, irishmoss, raw. April 2019. Available at: https://fdc.nal.usda.gov/fdc-app.html#/food-details/168456/nutrients. Accessed Aug. 30, 2022.
  3. Palmieri B, Vadalà M, Laurino C. Clinical effects of overwintered-stressed Chondrus Crispus and non-overwintered-stressed Chondrus crispus dietary supplementations. Asian J Med Sci. 2018; 9(6): 7-13. DOI

See these in context on the Sea Moss monograph →

Wild Lettuce 5 references
  1. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  3. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  4. Besharat S, Besharat M, Jabbari A. Wild lettuce (Lactuca virosa) toxicity. BMJ Case Rep. 2009;2009. pii: bcr06.2008.0134.
  5. Mullins ME, Horowitz BZ. The case of the salad shooters: intravenous injection of wild lettuce extract. Vet Hum Toxicol. 1998;40(5):290-1.

See these in context on the Wild Lettuce monograph →

Dulse 5 references
  1. Malta D, Arcand J, Ravindran A, Floras V, Allard JP, Newton GE. Adequate intake of potassium does not cause hyperkalemia in hypertensive individuals taking medications that antagonize the renin angiotensin aldosterone system. Am J Clin Nutr 2016 Oct;104(4 PubMed
  2. Allsopp P, Crowe W, Bahar B, et al. The effect of consuming Palmaria palmata-enriched bread on inflammatory markers, antioxidant status, lipid profile and thyroid function in a randomised placebo-controlled intervention trial in healthy adults. Eur J Nutr PubMed
  3. McGrath BM, Harmon JP, Bishop G. Palmaria palmata (Dulse) as an unusual maritime aetiology of hyperkalemia in a patient with chronic renal failure: a case report. J Med Case Rep. 2010;4:301. PubMed
  4. Furuta T, Miyabe Y, Yasui H, Kinoshita Y, Kishimura H. Angiotensin I converting enzyme inhibitory peptides derived from phycobiliproteins of dulse Palmaria palmata. Mar Drugs. 2016;14(2):32. PubMed
  5. Takase T, Nakamura A, Miyoshi H, et al. Effects of Palmaria palmata on lipid metabolism and glycemic control in participants with hypercholesterolemia in a randomized double-blind placebo-controlled trial. Phytother Res. 2020.

See these in context on the Dulse monograph →

Fucus Vesiculosus 15 references
  1. Goodman GA, Rall TW, Nies AS, Taylor P. The Pharmacological Basis of Therapeutics, 9th ed.
  2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002.
  3. Phaneuf D, Cote I, Dumas P, et al. Evaluation of the contamination of marine algae (Seaweed) from the St. Lawrence River and likely to be consumed by humans. Environ Res 1999;80:S175-S182. PubMed
  4. Durig J, Bruhn T, Zurborn KH, et al. Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro. Thromb Res 1997;85:479-91. PubMed
  5. Conz PA, La Greca G, Benedetti P, et al. Fucus vesiculosus: a nephrotoxic alga? Nephrol Dial Transplant 1998;13:526-7.
  6. Ohye H, Fukata S, Kanoh M, et al. Thyrotoxicosis caused by weight-reducing herbal medicines. Arch Intern Med 2005;165:831-4. PubMed
  7. Okamura K, Inoue K, Omae T. A case of Hashimoto's thyroiditis with thyroid immunological abnormality manifested after habitual ingestion of seaweed. Acta Endocrinol (Copenh) 1978;88:703-12. PubMed
  8. Agarwal SC, Crook JR, Pepper CB. Herbal remedies -- how safe are they? A case report of polymorphic ventricular tachycardia/ventricular fibrillation induced by herbal medication used for obesity. Int J Cardiol 2006;106:260-1. PubMed
  9. Sterling JB, Heymann WR. Potassium iodide in dermatology: a 19th century drug for the 21st century-uses, pharmacology, adverse effects, and contraindications. J Am Acad Dermatol 2000;43:691-7. PubMed
  10. Catania, M. A., Oteri, A., Caiello, P., Russo, A., Salvo, F., Giustini, E. S., Caputi, A. P., and Polimeni, G. Hemorrhagic cystitis induced by an herbal mixture. South.Med.J. 2010;103(1):90-92. PubMed
  11. Cumashi, A., Ushakova, N. A., Preobrazhenskaya, M. E., D'Incecco, A., Piccoli, A., Totani, L., Tinari, N., Morozevich, G. E., Berman, A. E., Bilan, M. I., Usov, A. I., Ustyuzhanina, N. E., Grachev, A. A., Sanderson, C. J., Kelly, M., Rabinovich, G. A., I
  12. Irhimeh, M. R., Fitton, J. H., and Lowenthal, R. M. Pilot clinical study to evaluate the anticoagulant activity of fucoidan. Blood Coagul.Fibrinolysis 2009;20(7):607-610. PubMed
  13. Arbaizar, B. and Llorca, J. [Fucus vesiculosus induced hyperthyroidism in a patient undergoing concomitant treatment with lithium]. Actas Esp.Psiquiatr. 2011;39(6):401-403.
  14. Church FC, Meade JB, Treanor RE, and et al. Antithrombin activity of fucoidan. The interaction of fucoidan with heparin cofactor II, antithrombin III, and thrombin. J Biol Chem 2-25-1989;264(6):3618-3623. DOI
  15. Mathew L, Burney M, Gaikwad A, et al. Preclinical evaluation of safety of fucoidan extracts from Undaria pinnatifida and Fucus vesiculosus for use in cancer treatment. Integr Cancer Ther 2017;16(4):572-84.

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DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

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