Herbal Tea Safety: Side Effects and Interactions to Know

Is herbal tea safe for most adults?

For most healthy adults, a cup of herbal tea in the evening is generally well tolerated. Herbal teas are not regulated like prescription medicines in the United States, so strength and purity can vary from product to product. That means the same herb may not deliver the same amount of active compounds in every cup.

The safety of a particular tea depends on the herb, how much and how often you drink it, the medications you take, your age and overall health, the number of medications or supplements you use, and whether you have liver, kidney, heart, bleeding, immune or mental health conditions. People taking sedatives or anti-anxiety medications, people on sleep medications, people who are pregnant or breastfeeding, and anyone with known plant allergies should consult a healthcare professional before use.

• Herbal teas are not overseen like regular medicines and may vary in strength and purity.
• Individual risk depends on the herb, dose, frequency, medications, age, health conditions, and other supplements.
• Check with a clinician or pharmacist if you take prescription medications, are pregnant or breastfeeding, or have a known plant allergy.

Sources: Nelson's Tea, Tea Runners, Texas Health Resources

Common side effects of calming herbs

Even gentle herbs can cause unwanted effects. Chamomile is often described as mildly relaxing rather than heavily sedating, but it may cause problems for people with allergies to related plants. Valerian root may be stronger and has been linked to vivid dreams, headaches, stomach upset, uneasiness, or drowsiness the next morning. Lavender is labeled by the FDA as generally recognized as safe, and few cautions appear in the available health-system guidance, though individual reactions are still possible.

• Chamomile: generally mild, but avoid if you are allergic to ragweed, daisies, marigolds or chrysanthemums.
• Valerian root: may cause vivid dreams, headaches, stomach upset, uneasiness, or next-morning drowsiness.
• Lavender: considered generally recognized as safe by the FDA; otherwise few cautions are reported in the available guidance.

Sources: Cleveland Clinic, Texas Health Resources, Health.com

Herb-drug interactions to consider

Herbal teas can affect how a medication is absorbed, metabolized, or excreted, or they may add to a medication's effects in unintended ways. Some interactions are well known. For example, St. John's wort is one of the best-known herbs for drug interactions and may reduce the effectiveness of several medications by speeding up the way the body breaks them down. Combining St. John's wort with medications that affect serotonin may increase the risk of serotonin toxicity, with warning signs such as tremor, agitation, sweating, diarrhea, confusion, muscle stiffness, fever or rapid heartbeat.

Other herbs carry different concerns. Chamomile may interact with the blood thinner warfarin and with cyclosporine, an immunosuppressant used to prevent organ rejection after transplant; it may also interact with drugs metabolized by the liver, such as sedatives. Valerian may increase drowsiness, especially when combined with prescription sleep medications, benzodiazepines or other anxiety medications, opioid pain medications, muscle relaxers, sedating antihistamines, or alcohol and other sedating substances. Combining valerian with sedating medications may increase the risk of extreme sleepiness, slowed reflexes, dizziness, confusion or falls, and people should not drive or operate machinery if they feel drowsy after using valerian.

Ginkgo may increase bleeding risk, especially for people taking anticoagulant or antiplatelet medications such as warfarin, aspirin, clopidogrel, ibuprofen or naproxen. People scheduled for surgery or procedures should tell their care team if they use ginkgo or any herbal products, because a clinician may recommend stopping certain herbal products before a procedure. Kava may interact with sedatives, antidepressants, anticonvulsants and other medications, and has also been associated with liver injury in some cases. People with liver disease or people taking medications that may affect the liver should avoid kava unless a clinician specifically says it is safe. Warning signs of liver problems can include unusual fatigue, nausea, loss of appetite, dark urine, pale stools, abdominal pain or yellowing of the skin or eyes; seek medical care promptly if these occur. Ginger tea may increase bleeding risk in some people, especially when used regularly or in large amounts with blood-thinning medications, and may also affect blood sugar or blood pressure in some cases.

• St. John's wort: may reduce effectiveness of several medications and increase risk of serotonin toxicity with serotonergic drugs.
• Valerian: additive drowsiness with sedatives, opioids, muscle relaxers, antihistamines, and alcohol; avoid driving if drowsy.
• Ginkgo: may increase bleeding risk with anticoagulants or antiplatelets; tell your care team before surgery.
• Kava: may interact with sedatives, antidepressants, anticonvulsants; associated with liver injury; avoid if you have liver disease.
• Chamomile: may interact with warfarin, cyclosporine, and liver-metabolized drugs such as sedatives.
• Ginger: may increase bleeding risk with blood thinners and may affect blood sugar or blood pressure.

Sources: Texas Health Resources, Health.com

Special populations: pregnancy, children, and older adults

Pregnancy and breastfeeding: The available guidance recommends that people who are pregnant or breastfeeding consult a healthcare professional before using calming herbal teas. Cleveland Clinic specifically advises that people who are pregnant or allergic to ragweed, daisies, marigolds or chrysanthemums should avoid chamomile tea. More detailed trimester-specific or dose-specific guidance for herbal tea use during pregnancy is not available in the sources reviewed here.

As with adults, a healthcare professional should be consulted before giving herbal teas to children, especially if they take medications or have health conditions.

Older adults: Older adults often take multiple medications, which can increase the chance of interactions. They may also be more sensitive to sedating effects. The general risk factors listed above—polypharmacy, age, and overall health—apply.

• Pregnant or breastfeeding: consult a healthcare professional; avoid chamomile if pregnant or allergic to related plants.
• Children: no specific guidance available; consult a healthcare professional before use.
• Older adults: higher risk due to multiple medications and increased sensitivity to sedation.

Sources: Cleveland Clinic, Tea Runners, Texas Health Resources

Signs of an allergic reaction

Allergic reactions to herbal teas are possible, especially if you are sensitive to related plants. For chamomile, people with allergies to ragweed, daisies, marigolds or chrysanthemums should avoid it. Signs of an allergic reaction can include rash, hives, itching, swelling of the lips, tongue or throat, difficulty breathing, or a drop in blood pressure. If you experience any of these symptoms after drinking an herbal tea, stop drinking it and seek medical attention promptly. If you have a known plant allergy, check with a healthcare professional before trying new herbal teas.

• Avoid chamomile if you are allergic to ragweed, daisies, marigolds or chrysanthemums.
• Watch for rash, hives, itching, swelling, difficulty breathing, or drop in blood pressure.
• Stop drinking the tea and seek medical attention if symptoms occur.

Sources: Cleveland Clinic, Texas Health Resources

Practical safety checklist for evening herbal tea

Use this checklist to make safer choices when you enjoy herbal tea as part of a calm evening routine.

1. Review your medications with a pharmacist or prescriber before regularly drinking herbal teas, especially sedatives, blood thinners, immunosuppressants, and antidepressants.
2. Start with a small amount to see how you respond, and avoid combining herbal teas with alcohol or other sedating substances.
3. If you are pregnant or breastfeeding, consult a healthcare professional; avoid chamomile if pregnant or allergic to related plants.
4. If you have a known plant allergy, check the herb's plant family and avoid related herbs.
5. If you feel drowsy after drinking valerian or other sedating herbs, do not drive or operate machinery.
6. Tell your care team about any herbal products you use before surgery or procedures.
7. Seek medical care promptly if you notice signs of liver problems (unusual fatigue, nausea, loss of appetite, dark urine, pale stools, abdominal pain, yellowing of the skin or eyes) or an allergic reaction.
8. If sleep problems persist for a week or two and falling asleep remains difficult, tea alone is not sufficient; seek additional help.

Sources: Cleveland Clinic, Texas Health Resources, Health.com

How much is too much?

There is no single daily limit that applies to all herbal teas. For most healthy adults, a general guide suggests that 2 to 4 cups of herbal tea per day is considered safe and typically healthy, but this figure comes from a secondary source that attributes it to a dietitian review; it is not a clinical guideline. The amount that is right for you depends on the specific herb, its strength, your medications, and your health. More concentrated forms, such as extracts or supplements, may have stronger effects than a brewed cup, so do not assume that a safe amount of tea translates to a safe amount of extract.

• A commonly cited general range is 2 to 4 cups per day for healthy adults, but this is not a clinical guideline.
• Pay attention to how you feel and adjust accordingly.
• Extracts and supplements may be stronger than brewed tea; do not assume equivalent safety.

Sources: Nelson's Tea, Health.com