Drug & supplement interaction

Guava + Clemastine

Clemastine brand name: Tavist Allergy.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Guava and Clemastine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Guava and Clemastine

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Clemastine and Guava in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Guava safety at a glance

Guava overall Use caution Guava fruit is generally safe as a food, but leaf extracts and supplements are less studied.
Pregnancy Use caution Guava fruit as a food is fine, but concentrated leaf supplements are not well studied and are best avoided.
Breastfeeding Likely Safe When guava fruit is consumed as food. There is insufficient reliable information available about the safety of guava fruit or leaf when used for medicinal purpo... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Clemastine and Guava? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Clemastine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Clemastine is filed under 4 classifications — including anticholinergic drugs, photosensitizing drugs, seizure threshold lowering drugs. Guava has documented interactions with 1 drug class — the most serious being antidiabetes drugs (moderate) — and none of Clemastine’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Guava Does Interact With Other Medications

Guava has 86 moderate known drug interactions in our database — Clemastine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 86 No known interaction 2,744 (incl. Clemastine)
Taking anything else?

Check Another of Your Medications Against Guava

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

What to actually watch for

No Interaction Found — But Data Suggests Guava and Clemastine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • A skin rash Additional detail

    Guava

    “Orally, guava leaf extract may cause transient abdominal pain or nausea. Topically, guava leaf extract may cause contact dermatitis.”

    Guava · Natural Medicines adverse-effect record, reported in dermatitis.

    2 sources cited
    1. 101782. Doubova SV, Morales HR, Hernández SF, et al. Effect of a Psidii guajavae folium extract in the treatment of primary dysmenorrhea: a randomized clinical trial. J Ethnopharmacol. 2007;110(2):305-10. PubMed
    2. 95560. Obi M, Miyazaki Y, Yokozeki H, Nishioka K. Allergic contact dermatitis due to guava tea. Contact Dermatitis. 2001;44(2):116-7. PubMed

    “Topically, guava leaf extract may cause contact dermatitis and worsen atopic dermatitis. Exacerbation of atopic dermatitis has been reported for a 17-year-old male who added tea bags containing guava leaf 30 grams to his bath to help treat his condition. His eczema worsened after bathing with the guava tea bags and improved after discontinuation of use.”

    Guava · Natural Medicines adverse-effect record, reported in dermatitis.

    1 source cited
    1. 95560. Obi M, Miyazaki Y, Yokozeki H, Nishioka K. Allergic contact dermatitis due to guava tea. Contact Dermatitis. 2001;44(2):116-7. PubMed

    Clemastine

    Listed in the ADVERSE REACTIONS section of the FDA label for Clemastine. Read the label on DailyMed ›

  • Nausea Additional detail

    Guava

    “Orally, transient abdominal pain or nausea has been reported in a clinical trial.”

    Guava · Natural Medicines adverse-effect record, reported in nausea and vomiting.

    1 source cited
    1. 101782. Doubova SV, Morales HR, Hernández SF, et al. Effect of a Psidii guajavae folium extract in the treatment of primary dysmenorrhea: a randomized clinical trial. J Ethnopharmacol. 2007;110(2):305-10. PubMed

    Clemastine

    Listed in the ADVERSE REACTIONS section of the FDA label for Clemastine. Read the label on DailyMed ›

Reported for Guava but not commonly for Clemastine: stomach pain.

Effects for Clemastine come from the ADVERSE REACTIONS section of its FDA label; effects for Guava come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Guava in Pregnancy & Breastfeeding

Lactation Likely Safe

When guava fruit is consumed as food. There is insufficient reliable information available about the safety of guava fruit or leaf when used for medicinal purposes during pregnancy and lactation.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Guava or Clemastine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Guava or Clemastine, 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 Clemastine

This page covers Guava only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Clemastine page lists 72 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Henbane (major), Scopolia (major), Alfalfa (moderate) and Angel's Trumpet (moderate).

By severity: 3 major · 57 moderate · 12 minor.

From our pharmacist’s overview on the Clemastine page

“Clemastine (Tavist Allergy) is an older, sedating antihistamine that already dries the mouth, blurs vision, and slows the gut, and that is exactly why this list earns real caution rather than a quick skim. Thirty of the 72 supplements on file pile the same drying, sedating anticholinergic load on top, and two of the three major-rated e…”

Reviewed by 2 · Jul 18, 2026

Open the Clemastine interaction page

One more smart check

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

We hold 484 real supplement products containing Guava, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Guava. Even though Guava itself has no known interaction with Clemastine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Guava and Clemastine 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 Guava
Top half

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

29 days ago today
Medication Clemastine
Steady interest

#2,051 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Guava reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Guava and Clemastine records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Guava

What is Guava?

  • Diarrhea and digestive upset
  • Blood sugar support
  • Cholesterol support
  • Wound and skin care
  • Cough and sore throat

Guava is a tropical fruit tree whose leaves and fruit have a long history of folk use for diarrhea, blood sugar, and general wellness. The fruit is a nutritious food rich in vitamin C, but evidence for guava leaf supplements treating specific health conditions is limited and mostly early. If you want to try guava leaf products, talk with your pharmacist or doctor first, especially if you take medicines or have a health condition.

Psidium guajava · Myrtaceae · Leaves, fruit, and bark · Tea, capsules, leaf extract, fresh fruit, juice, powder

An interaction check asks whether these two react with each other — it does not ask whether Guava is a good idea for someone in your situation. Here is what our Guava record says about it on its own.

Guava: dosing

There is no official, standardized dose for guava leaf supplements. The amount in products varies widely depending on the form (tea, capsule, or extract) and how concentrated it is.The best approach is to follow the directions on the product label and not exceed the recommended amount. Because quality and strength differ between brands, choose products from reputable companies.

From our Guava monograph — the full record covers uses, side effects and every documented interaction.

Read the full Guava monograph & all interactions
Medication

About Clemastine

What Is Clemastine Used For?

Brand name: Tavist Allergy

Clemastine treats symptoms of allergic rhinitis (hay fever and similar nasal allergies) — including sneezing, runny nose, itching, and watery eyes. The oral solution (Clemastine Fumarate syrup) is indicated for adults and children aged 6 through 12 years. The tablets (Clemastine Fumarate and Clemsza) are indicated for adults.

Clemastine also treats mild, uncomplicated allergic skin reactions — specifically urticaria (hives) and angioedema (swelling under the skin) — at the appropriate dosage level, in both the oral solution and tablet forms.

See full Clemastine drug information
Keep checking

Other Drugs & Guava

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

0Major
86Moderate
0Minor
2,743No known interaction
86 Moderate 2,743 No interaction
Moderate

86 interactions

Showing 60 of 86 moderate interactions — see all 86 on the Guava page.

No interaction 2,743 drugs checked — show the list

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

Showing the 60 most looked-up of 2,743 medications checked with no known interaction — see the full Guava list.

See the full Guava interactions page
See every supplement checked against Clemastine, ranked by severity
Evidence & sources

Guava References

The 7 references that drive our Guava monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Lozoya, X., Reyes-Morales, H., Chavez-Soto, M. A., Martinez-Garcia, Mdel C., Soto-Gonzalez, Y., and Doubova, S. V. Intestinal anti-spasmodic effect of a phytodrug of Psidium guajava folia in the treatment of acute diarrheic disease. J Ethnopharmacol 2002 PubMed
  2. Obi M, Miyazaki Y, Yokozeki H, Nishioka K. Allergic contact dermatitis due to guava tea. Contact Dermatitis. 2001;44(2):116-7. PubMed
  3. Singh RB, Rastogi SS, Singh R, Ghosh S, Niaz MA. Effects of guava intake on serum total and high-density lipoprotein cholesterol levels and on systemic blood pressure. Am J Cardiol. 1992;70(15):1287-91. PubMed
  4. Nayak N, Varghese J, Shetty S, et al. Evaluation of a mouthrinse containing guava leaf extract as part of comprehensive oral care regimen- a randomized placebo-controlled clinical trial. BMC Complement Altern Med. 2019;19(1):327. PubMed
  5. Kakuo S, Fushimi T, Kawasaki K, Nakamura J, Ota N. Effects of Psidium guajava Linn. Leaf extract in Japanese subjects with knee pain: a randomized, double-blind, placebo-controlled, parallel pilot study. Aging Clin Exp Res. 2018;30(11):1391-1398. PubMed
  6. Gutiérrez RM, Mitchell S, Solis RV. Psidium guajava: a review of its traditional uses, phytochemistry and pharmacology. J Ethnopharmacol. 2008;117(1):1-27. PubMed
  7. Doubova SV, Morales HR, Hernández SF, et al. Effect of a Psidii guajavae folium extract in the treatment of primary dysmenorrhea: a randomized clinical trial. J Ethnopharmacol. 2007;110(2):305-10. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Guava and Clemastine Together: Common Questions

Is it safe to take Guava with Clemastine?
We do not list a known interaction between Guava and Clemastine. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Guava and Clemastine have any of the same side effects?
Yes — our sources link each of them separately to 2 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Guava and Clemastine combination checked?
Interactions in our licensed database are recorded against drug classes. Clemastine is filed under 4 classifications, and Guava has documented interactions with 1 drug class — none of Clemastine's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Guava interact with any other medications?
Yes. Guava has 86 documented drug interactions in our database — Clemastine is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Clemastine interact with any supplements?
Yes. Clemastine has documented interactions with 72 supplements in our database — Guava is not one of them. The Clemastine interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Guava monograph Uses, safety profile, and every drug interaction in one place Clemastine drug information The full plain-English guide to this medication Clemastine supplement interactions Every supplement checked against Clemastine, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 7 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Clemastine and Guava?

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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.