Drug & supplement interaction

Thyme + Aspirin, Diphenhydramine, Phenylpropanolamine

Aspirin, Diphenhydramine, Phenylpropanolamine brand name: Alka Seltzer Plus Night Time Effervescent.

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

Aspirin, Diphenhydramine, Phenylpropanolamine falls into 2 drug categories that Thyme can interact with; the most serious is rated moderate. Theoretically, thyme leaf extract might have additive effects with anticoagulant or antiplatelet drugs.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Thyme and Aspirin, Diphenhydramine, Phenylpropanolamine

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Thyme interacts with whole categories of medication. Aspirin, Diphenhydramine, Phenylpropanolamine falls into 2 of those categories, so it can interact with Thyme in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

1 of 2

Why this applies to Aspirin, Diphenhydramine, Phenylpropanolamine

Aspirin, Diphenhydramine, Phenylpropanolamine falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Thyme interacts with.

Theoretically, thyme leaf extract might have additive effects with anticoagulant or antiplatelet drugs.
In vitro and animal research suggests that thyme leaf extract has antiplatelet effects. However, this effect has not been observed in humans.
Severity Moderate 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

This combination product (Alka Seltzer Plus Night Time) contains aspirin, which already thins the blood a bit by keeping platelets from sticking together. Thyme is the piece that matters here. In test tube and animal studies, thyme leaf extract showed a mild blood-thinning, anti-platelet action of its own. Stacked on top of aspirin, the theory is that the two could nudge your bleeding risk a little higher.

Here's my honest take: this is theoretical, and that anti-platelet effect has never actually been seen in people. The thyme you cook with or sip in a tea is not a concern. If you're using concentrated thyme supplements regularly, just mention it to your pharmacist or doctor, and watch for easy bruising, nosebleeds, or bleeding gums.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Okazaki K, Kawazoe K, Takaishi Y. Human platelet aggregation inhibitors from thyme (Thymus vulgaris L.). Phytother Res 2002;16:398-9. .
  2. Yamamoto J, Yamada K, Naemura A, et al. Testing various herbs for antithrombotic effect. Nutrition 2005;21(5):580-7. PubMed
  3. Tognolini, M., Barocelli, E., Ballabeni, V., Bruni, R., Bianchi, A., Chiavarini, M., and Impicciatore, M. Comparative screening of plant essential oils: phenylpropanoid moiety as basic core for antiplatelet activity. Life Sci. 2-23-2006;78(13):1419-1432. PubMed
Moderate

ANTICHOLINERGIC DRUGS

2 of 2

Aspirin, Diphenhydramine, Phenylpropanolamine also falls under ANTICHOLINERGIC DRUGS.

Theoretically, concurrent use of anticholinergic drugs and thyme essential oil might reduce the effects of anticholinergic drugs.
In vitro evidence suggests that thyme essential oil and specific essential oil constituents like thymohydroquinone and carvacrol can inhibit acetylcholinesterase (AChE). However, this effect has not been observed in humans.
Severity Moderate 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 for your Alka-Seltzer Plus Night Time, which contains the antihistamine diphenhydramine along with aspirin and phenylpropanolamine. Diphenhydramine works partly by blocking acetylcholine, so it has anticholinergic effects. In test-tube studies, compounds in thyme essential oil (like thymol and carvacrol) can nudge acetylcholine levels back up, which could in theory slightly blunt the antihistamine's action. Practically, that might mean a touch less drowsiness or dryness, but honestly this has only been seen in the lab, never in actual people.

Sprinkling thyme on dinner or sipping a thyme cough product won't realistically affect this medicine. I wouldn't lose sleep over it, but if you're using concentrated thyme oil, just mention it to your pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Jukic, M., Politeo, O., Maksimovic, M., Milos, M., and Milos, M. In vitro acetylcholinesterase inhibitory properties of thymol, carvacrol and their derivatives thymoquinone and thymohydroquinone. Phytother.Res 2007;21(3):259-261.

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

Thyme Also Interacts With Other Medications

Thyme has 378 moderate known drug interactions in our database — the Aspirin, Diphenhydramine, Phenylpropanolamine one above is among them. If you take anything else, check it against the full list below.

Moderate 378 No known interaction 2,452 (incl. Aspirin, Diphenhydramine, Phenylpropanolamine)
Taking anything else?

Check Another of Your Medications Against Thyme

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

Everything else you take

See Every Supplement That Interacts With Aspirin, Diphenhydramine, Phenylpropanolamine

This page covers Thyme only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Aspirin, Diphenhydramine, Phenylpropanolamine page lists 361 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), Asarabacca (major), Beer (major) and Danshen (major).

By severity: 17 major · 308 moderate · 36 minor.

From our pharmacist’s overview on the Aspirin, Diphenhydramine, Phenylpropanolamine page

“A cold remedy used for a few nights can still collide with supplements taken daily, and Alka Seltzer Plus Night Time (aspirin, diphenhydramine, phenylpropanolamine) is one to treat with genuine care. Its three ingredients thin the blood, sedate, and stimulate all at once, which is why 361 supplements and herbs are on file here.”

Reviewed by 2 · Jul 18, 2026

Open the Aspirin, Diphenhydramine, Phenylpropanolamine interaction page

One more smart check

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

We hold 708 real supplement products containing Thyme, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Thyme. Your product may carry other ingredients that interact with Aspirin, Diphenhydramine, Phenylpropanolamine too, on top of Thyme — 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 Thyme and Aspirin, Diphenhydramine, Phenylpropanolamine 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 Thyme
Top 25%

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

29 days ago today
Medication Aspirin, Diphenhydramine, Phenylpropanolamine
Top half

#1,317 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 Thyme

What is Thyme?

Thyme
  • Cough and respiratory congestion
  • Sore throat
  • Digestive upset
  • Antimicrobial and antiseptic uses
  • Flavoring in cooking

Thyme is a common kitchen herb that has long been used for coughs, sore throats, and digestive complaints. It is generally safe in the amounts found in food, and some cough products that combine thyme with other herbs have modest supporting evidence, but high-quality research on thyme alone is limited. The concentrated essential oil should never be swallowed undiluted.

Read the full Thyme monograph & all interactions
Keep checking

Other Drugs & Thyme

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

0Major
378Moderate
0Minor
2,451No known interaction
378 Moderate 2,451 No interaction
Moderate

378 interactions

Showing 60 of 378 moderate interactions — see all 378 on the Thyme page.

No interaction 2,451 drugs checked — show the list

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

Showing the 60 most looked-up of 2,451 medications checked with no known interaction — see the full Thyme list.

See the full Thyme interactions page
See every supplement checked against Aspirin, Diphenhydramine, Phenylpropanolamine, 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
Thyme monograph › Uses, safety, and every drug interaction in one place Aspirin, Diphenhydramine, Phenylpropanolamine supplement interactions › Every supplement checked against Aspirin, Diphenhydramine, Phenylpropanolamine, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Thyme and Aspirin, Diphenhydramine, Phenylpropanolamine Together: Common Questions

Can you take Thyme with Aspirin, Diphenhydramine, Phenylpropanolamine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Thyme and Aspirin, Diphenhydramine, Phenylpropanolamine?
Aspirin, Diphenhydramine, Phenylpropanolamine belongs to more than one drug category, and Thyme interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Thyme and Aspirin, Diphenhydramine, Phenylpropanolamine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Aspirin, Diphenhydramine, Phenylpropanolamine and Thyme?

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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.