Drug & supplement interaction

Algin + Diphenhydramine

Diphenhydramine brand names: Benadryl, Dormin, Allerdryl, Valdrene, Sleep-Ettes D, and others.

Minor Interaction
Medically reviewed by · Updated September 2026
The bottom line Minor

Algin has a minor interaction with Diphenhydramine. Theoretically, algin can alter the absorption of oral drugs.

Read the full interaction report
SeverityMinor
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Algin and Diphenhydramine

Here is the interaction we found between these two, with the evidence behind it.

Minor

ORAL DRUGS

Why this applies to Diphenhydramine

Diphenhydramine falls under ORAL DRUGS — the group Algin interacts with.

Theoretically, algin can alter the absorption of oral drugs. Laboratory research shows that algin, when consumed as part of the diet or used as a thickening agent in infant formula, reduces the absorption of certain minerals. Also, algin has been used as a tablet binder and disintegrant to enhance drug bioavailability. To avoid changes in absorption, take algin 30-60 minutes after oral medications.
Severity Minor Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with Algin and your diphenhydramine (Benadryl). Algin is a seaweed fiber that soaks up water and forms a thick gel in your stomach. In theory, that gel could grab onto a pill you swallow and slow down or slightly lower how much of the drug your body absorbs. For diphenhydramine, that might mean it works a touch less reliably, so your allergy relief or sleep help could feel a little weaker or come on slower.

This is only a theoretical concern based on how algin behaves, not something proven in people taking this combo. An easy fix is simple timing: take your diphenhydramine first, then wait 30 to 60 minutes before the algin. If you're unsure, your pharmacist can help you space them out.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Harmuth-Hoene, A. E. and Schelenz, R. Effect of dietary fiber on mineral absorption in growing rats. J Nutr 1980;110(9):1774-1784. PubMed
  2. Bosscher D, Van Caillie-Bertrand M, Deelstra H. Effect of thickening agents, based on soluble dietary fiber, on the availability of calcium, iron, and zinc from infant formulas. Nutrition. 2001;17(7-8):614-8. PubMed
  3. Beneke CE, Viljoen AM, Hamman JH. Polymeric plant-derived excipients in drug delivery. Molecules. 2009;14(7):2602-20. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Algin Also Interacts With Other Medications

Algin has 2,021 minor known drug interactions in our database — the Diphenhydramine one above is one of them. If you take anything else, check it against the full list below.

Minor 2,021 No known interaction 809 (incl. Diphenhydramine)
Taking anything else?

Check Another of Your Medications Against Algin

Covers the 2,830 medications we’ve checked against Algin. Pick one to open its full report.

From our Q&A

Questions About Algin or Diphenhydramine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Algin or Diphenhydramine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Diphenhydramine

This page covers Algin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Diphenhydramine page lists 147 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Henbane (major).

By severity: 9 major · 119 moderate · 19 minor.

From our pharmacist’s overview on the Diphenhydramine page

“Diphenhydramine (Benadryl, Simply Sleep) is sedating by design, and most of the 147 supplements and herbal ingredients on this list lean into that. Seventy-eight are sedating substances themselves, alcohol and kava the standouts, and stacking them can slow breathing and reflexes well beyond ordinary drowsiness.”

Reviewed by 2 · Jul 18, 2026

Open the Diphenhydramine interaction page

One more smart check

Taking Algin as Part of a Dietary Supplement Product? Check It for Interactions

We hold 60 real supplement products containing Algin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Algin. Your product may carry other ingredients that interact with Diphenhydramine too, on top of Algin — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Algin and Diphenhydramine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Algin
Top half

#424 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Diphenhydramine
Top half

#739 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Algin

What is Algin?

Algin
  • Heartburn and acid reflux (in combination products)
  • Lowering cholesterol
  • Digestive health and feeling full
  • Use as a thickener and binder in foods and medicines
  • Weight management

Algin (alginate) is a fiber-like substance from brown seaweed that is widely used as a thickener, gel, and binder in foods and medicines. Its best-known medical use is in heartburn products, where it forms a barrier that helps reduce acid reflux; evidence for other uses like lowering cholesterol or weight loss is weaker. It is generally considered safe in food amounts, but check with your pharmacist before using it as a supplement, especially if you are pregnant or breastfeeding.

Read the full Algin monograph & all interactions
Medication

About Diphenhydramine

What Is Diphenhydramine Used For?

Brand names: Benadryl, Dormin, Allerdryl, Valdrene, Sleep-Ettes D, Simply Sleep, Sominex, Diphenhydramine, Compoz, Sleep Aid, Benadryl cream, Benadryl spray, Dermamycin cream, Ziradryl, Nytol

Diphenhydramine temporarily relieves symptoms of hay fever, other upper respiratory allergies, and the common cold — including runny nose, sneezing, itchy or watery eyes, and itching of the nose or throat.

After Bite Xtra gel is formulated for topical use and is approved to temporarily relieve pain and itching from minor burns, minor cuts and scrapes, insect bites, minor skin irritations, and rashes from poison ivy, poison oak, and poison sumac.

See full Diphenhydramine drug information
Keep checking

Other Drugs & Algin

Browse every other medication we’ve checked against Algin — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
2,021Minor
808No known interaction
2,021 Minor 808 No interaction
Minor

2,021 interactions

Showing 60 of 2,021 minor interactions — see all 2,021 on the Algin page.

No interaction 808 drugs checked — show the list

We also checked Algin against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 808 medications checked with no known interaction — see the full Algin list.

See the full Algin interactions page
See every supplement checked against Diphenhydramine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

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

Parts of this content are provided by the Therapeutic Research Center, LLC.

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.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Algin monograph › Uses, safety, and every drug interaction in one place Diphenhydramine supplement interactions › Every supplement checked against Diphenhydramine, ranked by severity Diphenhydramine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Algin and Diphenhydramine Together: Common Questions

Can you take Algin with Diphenhydramine?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Algin and Diphenhydramine interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Diphenhydramine and Algin?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.