Eugenol belongs to the Phenol chemical family. Phenols are potentially irritating components to the skin and mucous membranes, and they can cause dermatitis and sensitization. If phenols are present in high concentrations in the essential oil, the essential oil should be used in very low dilutions on the skin, diluted well in carrier oil, and only used for short
periods of time.
Phenol-high oils are skin irritating if used in a bath.
Use in small amounts when blending phenol-rich oils for diffusing (no more than 10% of the pure essential oil blend).
Phenol-rich oils should not be used on people with skin issues such as dermatitis, or on babies or children.
Oils high in eugenol, thymol or carvacrol inhibits platelet aggregation, and are not to be used by people with blood clotting disorders, by people taking anticoagulant drugs such as aspirin or Warfarin, or before surgery. According to Tisserand, Holy basil may inhibit blood clotting, have skin sensitization effects & possible mucous membrane irritation.
Suggested maximum topical use of eugenol is 0.5%. In small doses, eugenol can be liver-protective, however, in high concentrations, it is hepatotoxic and can cause tissue damage.
Maximum dermal level 1.0% (based on 50.4% eugenol content with a dermal limit of 0.5%