Chamomile Safety & Interactions: Who Should Be Cautious

Chamomile has a reputation as the gentlest thing in the cupboard. For most people, that reputation is earned — it's one of the better-tolerated botanicals in common use, and serious problems are rare.

But "rare" isn't "never," and chamomile has a specific set of risks that are genuinely worth knowing. There's a documented case of internal bleeding in a patient combining it with a blood thinner. There are anaphylaxis cases from a single cup of tea. And the allergy risk extends to a plant most people wouldn't think to connect it to.

This article covers what's actually documented, and who should talk to a doctor first.

The Overall Picture

A 2025 systematic review of chamomile adverse events pooled seventy-two clinical trials and eleven case reports. Across trials in which 2,896 patients received chamomile, 65 adverse events were reported. The most common were gastrointestinal complaints and drowsiness, both self-limiting and non-serious.

Notably, no allergic adverse events appeared in the clinical trials at all. But among the eleven case reports, six involved allergic reactions — three of them anaphylactic.

That gap between the trial data and the case reports is the most useful thing in the review, and it explains the shape of chamomile's risk profile. Trials enroll relatively healthy, screened participants over short periods. Case reports capture what happens in the real world, where nobody screens for a ragweed allergy before making tea.

The review's authors also flagged a reporting problem: roughly a third of the trials provided no adverse event data at all, and most did not report the purity or potency of the chamomile products they tested. The safety literature here is thinner than the number of studies suggests.

Allergy: The Main Real-World Risk

Chamomile is in the Asteraceae family — also called Compositae — alongside ragweed, chrysanthemums, marigolds, and daisies. The National Center for Complementary and Integrative Health notes that people allergic to those related plants are more likely to react to chamomile, and that reactions can include severe hypersensitivity and anaphylaxis.

Memorial Sloan Kettering's About Herbs database states the contraindication directly: individuals allergic to ragweed or members of the Compositae family should avoid chamomile. Documented hypersensitivity reactions include asthma, contact dermatitis, and anaphylaxis.

The Mugwort Connection. This is the one most people miss. MSK also lists mugwort pollen allergy as a contraindication, noting multiple documented cases of cross-reaction. In one published case, a 65-year-old woman with mugwort pollinosis developed hives, vomiting, and shortness of breath thirty minutes after drinking chamomile tea; roughly a dozen other reported allergic reactions to chamomile have been linked to mugwort pollen allergy. She was advised to avoid all chamomile-containing products.

If you have mugwort allergy, treat chamomile as off-limits until you've talked to an allergist. This isn't a well-known association and it doesn't appear on most product labels.

Anaphylaxis is documented, not theoretical. A published case describes a 38-year-old man who developed severe anaphylaxis — generalized urticaria, angioedema, and severe difficulty breathing — one hour after drinking chamomile tea, requiring intravenous antihistamines.

These events are rare relative to how much chamomile is consumed worldwide. But they are real, they have followed a single cup of ordinary tea, and anyone with a known daisy-family or mugwort allergy should take them seriously.

Drug Interactions

Blood thinners — the most important one

Chamomile contains coumarin compounds, and MSK notes it may increase anticoagulant effects and inhibit platelet activity.

This is not just theoretical. A published case report in the Canadian Medical Association Journal describes a 70-year-old woman who developed multiple internal hemorrhages following concurrent use of chamomile products and warfarin. Her symptoms resolved after treatment with intravenous heparin.

NCCIH independently lists warfarin among the interactions reported with chamomile. MSK's patient-facing guidance is to talk to your provider if you take blood thinners such as warfarin, because chamomile may increase bruising and bleeding risk.

If you take warfarin, an antiplatelet drug, or any anticoagulant, this is a conversation to have before you start drinking chamomile regularly — not after.

Drugs metabolized by the liver

In laboratory testing, chamomile essential oil inhibits several cytochrome P450 enzymes — CYP1A2, CYP2C9, CYP2D6, and CYP3A4 — which between them metabolize a very large share of common medications. Inhibiting them could raise circulating drug levels.

The honest caveat, which MSK states plainly: the clinical relevance of this has yet to be determined. These are in vitro findings, and in vitro inhibition doesn't always translate to a meaningful effect in a person drinking tea. NCCIH's language is similarly measured — interactions with some drugs metabolized by the liver have been reported.

Take it as a reason to mention chamomile to your prescriber, not a reason to panic.

Cyclosporine

Concurrent use of chamomile and cyclosporine — an immunosuppressant used to prevent transplant rejection — resulted in increased serum cyclosporine levels in reported cases. For transplant recipients, where cyclosporine levels are carefully titrated, this matters a great deal.

Sedatives

MSK notes chamomile may increase the effects of sedatives. NCCIH describes this as a theoretical concern rather than a demonstrated one. Either way, if you take a prescription sleep aid or benzodiazepine, mention it.

Hormonal birth control

NCCIH reports that chamomile might have some of the same effects as estrogen, and that preliminary studies suggest taking chamomile alongside birth control pills might decrease the pills' effectiveness. The same estrogen-like activity is why NCCIH advises that chamomile might worsen conditions sensitive to estrogen exposure, including breast and uterine cancer.

Population-Specific Guidance

Pregnancy. NCCIH states that little is known about whether chamomile is safe during pregnancy. There is also a published case report of premature constriction of the fetal ductus arteriosus — a serious cardiovascular complication in a developing fetus — following maternal consumption of chamomile herbal tea. One case is not a pattern, but combined with the absence of safety data, the sensible position is to talk to your obstetric provider before drinking chamomile during pregnancy.

Breastfeeding. Also largely unstudied. One published case reported increased lactogenesis and breast tension in a lactating woman a few hours after consuming chamomile. Worth discussing with your provider.

People with estrogen-sensitive conditions. Given the possible estrogen-like activity, NCCIH advises caution for conditions including breast and uterine cancer.

Children. NCCIH notes that combination products containing chamomile have been studied for colic and childhood diarrhea, but chamomile alone hasn't been shown helpful for these. Given that allergy risk applies to children as much as adults — and that a child can't easily describe early symptoms — check with a pediatrician first.

People with occupational exposure. There's a documented case of allergic rhinoconjunctivitis caused by inhaling dried chamomile flowers. If you handle bulk dried botanicals regularly, that's a different exposure route worth knowing about.

Key Takeaways

• Chamomile is well tolerated by most people; trial adverse events are mild, mostly GI upset and drowsiness.
• Allergy is the primary real risk. Avoid chamomile if you're allergic to ragweed, chrysanthemums, marigolds, daisies, or mugwort.
• Anaphylaxis from chamomile tea is documented in published case reports, though rare.
• Warfarin and other anticoagulants carry the most serious documented interaction — including a case of multiple internal hemorrhages.
• Cyclosporine levels rose with concurrent chamomile use; relevant for transplant patients.
• CYP450 inhibition is an in vitro finding of undetermined clinical significance.
• Pregnancy and breastfeeding are unstudied, with one case report of fetal ductus arteriosus constriction.
• If you take any regular medication, tell your prescriber you're drinking chamomile.

When to Talk to a Doctor First

Before adding chamomile to a regular routine, check with a healthcare provider if you:

• Have any allergy to ragweed, mugwort, daisies, chrysanthemums, or marigolds
• Take warfarin, another anticoagulant, or an antiplatelet drug
• Take cyclosporine or another immunosuppressant
• Take hormonal birth control
• Have a hormone-sensitive condition
• Take a sedative or prescription sleep medication
• Are pregnant or breastfeeding
• Are considering giving it to a child

And if you experience hives, swelling of the lips or throat, wheezing, or difficulty breathing after chamomile, stop and seek medical care immediately.

Why We're Telling You This

We sell chamomile. It would be easier to leave this article unwritten and let the "gentlest herb in the cupboard" reputation do the work.

But a person on warfarin who doesn't know about the coumarin interaction, or someone with mugwort allergy who's never seen it connected to chamomile, is exactly the customer we'd rather inform than sell to. The risks here are manageable and mostly avoidable — but only if somebody says them out loud.

Frequently Asked Questions

Who should not drink chamomile tea?

Anyone with a known allergy to ragweed, mugwort, chrysanthemums, marigolds, or daisies. Anyone taking warfarin or another anticoagulant should check with a provider first, as should people taking cyclosporine, hormonal birth control, or sedatives, and anyone pregnant or breastfeeding.

Can chamomile cause an allergic reaction?

Yes. Reactions range from contact dermatitis and asthma to anaphylaxis. Published case reports document severe anaphylaxis following a single cup of chamomile tea, though these events are rare.

Does chamomile interact with blood thinners?

There is a documented interaction. Chamomile contains coumarin compounds that may increase anticoagulant effects, and a published case report describes multiple internal hemorrhages in a patient using chamomile alongside warfarin.

Is chamomile safe during pregnancy?

It hasn't been adequately studied, and there's a published case of premature constriction of the fetal ductus arteriosus following maternal chamomile tea consumption. Talk to your obstetric provider.

Why does mugwort allergy matter for chamomile?

Cross-reactivity is documented — roughly a dozen reported allergic reactions to chamomile have been associated with mugwort pollen allergy. It's a less well-known connection than the ragweed one, and worth knowing if you have mugwort sensitivity.

How much chamomile is too much?

No dose-response relationship for adverse events has been established, partly because trials rarely reported product purity or potency. NCCIH considers chamomile likely safe in the amounts commonly found in teas and foods; medicinal-strength preparations are a different question.

Can children drink chamomile tea?

Combination products containing chamomile have been studied in children, but chamomile alone hasn't been shown effective for the conditions it's used for. The allergy risk applies to children too. Check with a pediatrician first.

Does chamomile affect other medications?

Possibly. Chamomile inhibits several CYP450 liver enzymes in laboratory testing, which could affect drugs metabolized by them — though the clinical significance of that finding hasn't been determined. Tell your prescriber either way.

Related Reading

• German vs. Roman Chamomile: What's the Difference?
• Echinacea Safety & Interactions: What to Know Before You Brew
• Is Mullein Leaf Safe? Dosage, Side Effects & Who Should Consult a Doctor

Sources

• National Center for Complementary and Integrative Health, National Institutes of Health. Chamomile: Usefulness and Safety. Last updated November 2024.
• Memorial Sloan Kettering Cancer Center, Integrative Medicine. Chamomile: Purported Benefits, Side Effects & More.
• Segal R, Pilote L. Warfarin interaction with Matricaria chamomilla. CMAJ. 2006;174(9):1281-1282.
• Nakagawa M, Hanada M, Amano H. A case of anaphylactic reaction to chamomile tea in a patient with mugwort pollinosis. Allergology International. 2019;68(3):396-398.
• Andres C, Chen WC, Ollert M, et al. Anaphylactic reaction to camomile tea. Allergology International. 2009;58(1):135-136.
• Sridharan S, Archer N, Manning N. Premature constriction of the fetal ductus arteriosus following the maternal consumption of camomile herbal tea. Ultrasound in Obstetrics & Gynecology. 2009;34(3):358-359.
• Ganzera M, Schneider P, Stuppner H. Inhibitory effects of the essential oil of chamomile (Matricaria recutita L.) and its major constituents on human cytochrome P450 enzymes. Life Sciences. 2006;78(8):856-861.
• Colombo D, Lunardon L, Bellia G. Cyclosporine and herbal supplement interactions. Journal of Toxicology. 2014;2014:145325.
• Ostovar M, et al. Chamomile: a systematic review of adverse events. Complementary Therapies in Medicine. 2025.

This article is for educational purposes only and is not intended as medical advice. Chamomile is not a treatment or cure for any condition. Talk with your healthcare provider before using chamomile, especially if you are pregnant, nursing, taking medication, managing an allergy, or considering it for a child. If you experience swelling, wheezing, or difficulty breathing after consuming chamomile, seek medical care immediately.