Lemon balm is safe for most adults when used in typical amounts. The U.S. Food and Drug Administration classifies lemon balm leaf extract as Generally Recognized As Safe (GRAS) for use as a flavoring agent in food, and clinical studies have used it at doses up to several grams per day without serious problems. That said, there are specific situations, medications, and health conditions where lemon balm warrants caution.
Common Side Effects
When taken by mouth, the most frequently reported side effect is drowsiness. This makes sense given that lemon balm is often used specifically for its calming properties, but it can catch you off guard if you’re not expecting it, especially during the daytime or before driving.
When applied to the skin, some people experience redness, irritation, or burning at the application site. Contact dermatitis (an itchy, inflamed skin reaction) has also been documented. Less common but more serious reactions include nausea, vomiting, stomach cramps, and dizziness. These tend to occur at higher doses. If you develop signs of an allergic reaction like difficulty breathing or swelling, stop using it immediately.
Typical Dosage Ranges
Most clinical research and herbal references point to a few standard forms. For tea, the usual amount is 1.5 to 4.5 grams of dried leaf steeped in about 150 milliliters of hot water, taken as needed. Tinctures (liquid extracts in alcohol) are typically used at 2 to 6 milliliters, three times daily. Topical creams containing a 1% concentrated extract are applied two to four times daily for up to 14 days, often for cold sores.
One important gap in the research: the safety of doses above 5,000 milligrams per day or supplementation lasting longer than about 8 weeks hasn’t been well studied. If you’re planning to use lemon balm daily over months, there simply isn’t strong long-term data to draw from.
Thyroid Medication Interactions
Lemon balm may affect thyroid hormone levels. This is a theoretical concern based on laboratory and animal research suggesting it can interfere with how the thyroid functions. If you have a thyroid condition like Graves’ disease or hypothyroidism, or if you take medication to regulate your thyroid, you should talk to your doctor before adding lemon balm to your routine. The interaction could potentially alter how well your medication works.
Interactions With Sedatives
Because lemon balm has mild sedative properties on its own, combining it with prescription sedatives can amplify drowsiness. This includes medications prescribed for insomnia or anxiety. Animal studies have shown that lemon balm increased the sleep-inducing effects of certain sedative drugs. No human studies have formally evaluated these interactions, but the risk of excessive drowsiness is real enough to be cautious. If you take any medication that causes sleepiness, check with your pharmacist or doctor before using lemon balm supplements.
Pregnancy and Breastfeeding
The safety picture during pregnancy and breastfeeding is incomplete. While lemon balm has GRAS status as a food flavoring, that classification covers the small amounts used to flavor food, not the larger doses found in supplements or concentrated extracts. No clinical studies have directly assessed its safety in pregnant women.
For breastfeeding, lemon balm has a traditional reputation as a milk-promoting herb, though the evidence for that is weak. More importantly, no data exists on whether its active compounds pass into breast milk or what effect they might have on a nursing infant. The Drugs and Lactation Database notes this gap explicitly. The practical takeaway: a cup of lemon balm tea is likely fine, but concentrated supplements are a different story during pregnancy or nursing.
Safety in Children
Lemon balm has been used in a limited number of pediatric studies. A combination product containing 80 milligrams of lemon balm extract and 160 milligrams of valerian has been studied as a sleep aid in children. Separately, a multi-herb preparation containing lemon balm showed improved symptoms in babies with colic. However, the overall evidence base is thin, and the product has not been sufficiently studied to confirm safety in children younger than 2 years of age.
Topical Use for Cold Sores
Lemon balm cream is widely used in Europe for herpes cold sores, applied at the first sign of a flare-up or used regularly for prevention. It’s also applied to minor wounds, skin irritations, and insect bites. The main risk with topical use is contact dermatitis, which affects a small number of users. If you notice increasing redness or itching around the application area rather than improvement, the cream itself may be the problem. Patch-testing on a small area of skin first is a simple way to check your tolerance.
Before Surgery
Because of its sedative properties and potential interactions with anesthesia and other medications used during surgery, it’s generally a good idea to stop taking lemon balm supplements at least two weeks before a scheduled procedure. This is standard guidance for most herbal supplements with sedative effects, since they can unpredictably interact with the drugs used during and after surgery.