Allergic reactivity for different dilutions of eugenol in repeated open application test and patch testing

Area of Science:

• Dermatology
• Allergology
• Contact Dermatitis

Background:

• Eugenol is a recognized contact sensitizer.
• It is a component of Fragrance Mix I, commonly used in consumer products.

Purpose of the Study:

• To evaluate allergic reactivity to eugenol using patch testing and repeated open application tests (ROAT).
• To determine the lowest concentration of eugenol that elicits an allergic response.

Main Methods:

• 67 subjects from 6 European dermatology clinics participated.
• Patch tests with 17 eugenol dilutions (2.0%-0.00006%) were performed before and after a 21-day ROAT.
• ROAT involved applying 3 eugenol dilutions (2.7%-0.5%) twice daily.

Main Results:

• 34 subjects had confirmed contact allergy to eugenol.
• Before ROAT, 61.8% showed a positive patch test, with the lowest positive concentration at 0.031%.
• ROAT was positive in 55.9% of allergic subjects; reaction time correlated inversely with eugenol concentration and allergic reactivity.

Conclusions:

• Eugenol can induce positive patch test reactions at very low doses.
• Eugenol hypersensitivity can persist even when previous patch tests are not reproducible.
• ROAT can reveal sensitization missed by non-reproducible patch tests.