Eugenol, the compound that gives cloves their distinctive smell and flavor, is safe at the small amounts found in food and most consumer products. The World Health Organization sets an acceptable daily intake of up to 2.5 mg per kilogram of body weight, and the U.S. FDA lists it as a permitted food additive used as a flavoring agent. Problems arise at higher concentrations, particularly with undiluted clove oil, which can cause serious harm if swallowed or applied directly to tissue.
Safety in Food and Flavoring
Eugenol occurs naturally in cloves, cinnamon, basil, and nutmeg. At the levels present in spices, teas, and flavored foods, it poses no health risk for most people. The WHO’s Joint Expert Committee on Food Additives reviewed the evidence and established a safe daily intake of 0 to 2.5 mg per kilogram of body weight. For a 150-pound adult, that works out to roughly 170 mg per day, far more than you’d get from normal cooking or seasoning.
At low concentrations, eugenol actually has useful properties. It acts as an antioxidant, has anti-inflammatory effects, and can inhibit certain bacteria and viruses. These benefits show up in lab studies at concentrations below about 60 micrograms per milliliter. Above that threshold, the compound flips from protective to damaging, generating harmful reactive oxygen species in cells instead of neutralizing them.
Where Toxicity Starts
The danger with eugenol is concentrated forms, mainly clove essential oil, which is 60 to 90 percent eugenol by weight. Swallowing even a small amount of undiluted clove oil can be toxic, especially for children. Overdose cases in the medical literature involve ingestions of 8 to 30 milliliters of clove oil, roughly one to two tablespoons. Within hours, victims develop agitation, declining consciousness, seizures, and coma.
Liver damage is the most serious consequence. In one case, a 3-month-old who swallowed about 8 milliliters of clove oil developed acute liver failure within a day, with liver enzyme levels spiking to more than 100 times normal. A 15-month-old who ingested 10 to 20 milliliters experienced similar liver enzyme spikes along with kidney dysfunction and dangerous blood acidity. Both children ultimately recovered over one to three weeks with hospital treatment, but these cases illustrate how narrow the margin is between a harmless flavoring dose and a life-threatening one.
At normal dietary doses, eugenol has never been shown to cause elevated liver enzymes or clinically apparent liver injury in humans. The toxicity risk is specific to concentrated oil ingestion.
Dental Uses
Dentists have used eugenol for over a century, typically mixed with zinc oxide to create temporary fillings and cements. When this mixture sits in a cavity, small amounts of eugenol seep through the tooth’s inner layer to reach the pulp. At low concentrations, it works as a mild anti-inflammatory and local anesthetic, which is why it can soothe a toothache and support healing.
The catch is that higher concentrations are directly toxic to living tissue. If pure eugenol contacts exposed pulp (the soft interior of the tooth), it can cause extensive tissue damage. Some root canal sealants containing eugenol have also been shown to be toxic to nerve cells. This is why dental professionals apply it in controlled formulations rather than in its pure form, and why over-the-counter clove oil products for toothache relief should be used sparingly and never poured directly into an open cavity.
Skin and Fragrance Products
Eugenol is a recognized skin sensitizer, meaning repeated exposure can trigger allergic contact dermatitis in some people. The European Union requires it to be listed on ingredient labels for cosmetics and fragrances when it exceeds certain concentrations, precisely because of this allergy risk.
The International Fragrance Association restricts eugenol levels in consumer products based on how much skin contact the product involves. Deodorants, which sit on skin all day, are limited to 0.2 mg per square centimeter per day. Perfumes allow up to 0.5 mg, and hand creams are capped at the same level. If you’ve ever noticed redness or itching from a perfume or scented lotion, eugenol is one of the more common fragrance allergens worth checking for on the label.
Risks During Pregnancy
Essential oil compounds like eugenol can cross the placenta into fetal circulation because they are small, fat-soluble molecules that bind easily to proteins. They also pass into breast milk through passive diffusion. While no human clinical trials have tested eugenol’s reproductive toxicity directly (for obvious ethical reasons), animal studies on certain essential oil constituents have shown embryotoxic effects.
The current expert consensus is cautious: essential oils and their concentrated constituents that have shown reproductive toxicity in animals should either be strictly avoided or used with caution during pregnancy and breastfeeding. This applies to concentrated clove oil supplements or aromatherapy products, not to cloves in your cooking. The trace amounts in food are not a concern.
Children and Accidental Ingestion
Nearly all severe eugenol poisoning cases in the medical literature involve young children who accidentally swallowed clove oil. A 7-month-old who was given clove oil orally (likely as a teething remedy) developed central nervous system depression, urinary abnormalities, and dangerous blood acidity. The toddler cases mentioned earlier involved liver failure requiring intensive care.
Children are especially vulnerable because their smaller body weight means even a few milliliters represents a massive dose relative to their size. If you keep clove oil at home for toothaches or aromatherapy, store it out of reach just as you would any medication. Clove oil should not be applied to infants’ gums as a teething remedy. Safer alternatives exist, and the risk of accidental ingestion or tissue irritation is too high.
Practical Thresholds to Keep in Mind
- Food and spices: Safe. Normal culinary use falls well below the WHO’s daily intake limit.
- Clove oil for toothache: Safe in tiny, diluted amounts applied to a cotton ball and held briefly against the tooth. Never swallow it, and avoid contact with open tissue.
- Fragrances and skincare: Safe for most people at regulated levels, but worth watching if you have sensitive skin or fragrance allergies.
- Undiluted clove oil, swallowed: Dangerous. As little as 5 to 10 milliliters can cause seizures, coma, and liver failure, particularly in children.
- Pregnancy: Avoid concentrated clove oil products. Cloves in food are fine.
The pattern is consistent: eugenol is safe and even beneficial at low, dietary-level concentrations, but it becomes toxic when concentrated and taken in large amounts or applied directly to living tissue. The compound itself isn’t inherently dangerous. The dose and the form determine the risk.