Active sensitization and contact allergy to methyl 2-octynoate.

Background: Methyl 2-octynoate is a synthetic fragrance which was first described to have sensitizing properties in 1935. It is one of the 26 fragrances to be labelled on the ingredient list according to current European cosmetics regulation.

Objectives: To report the experience with patch testing with methyl 2-octynoate 1% and 2% in pet.

Methods: 230 eczema patients were consecutively patch tested with 1% methyl 2-octynoate at department of Dermato-allergology Gentofte Hospital, Denmark and 120 eczema patients were consecutively patch tested with 2% M2O in Finn Chambers at the Départment de Dermatologie, CHU Saint Jacques, France.

Results: Three cases of active sensitization were observed. 2 (0.87%) of the 230 Danish subjects tested with 1% in pet. and of the 120 French subjects patch tested with 2% in pet. 1 (0.83%). There was no statistical difference in active sensitization between the two groups (P = 0.72). Allergic contact dermatitis was observed in two patients (1.67%) in the French group and none in the Danish group.

Conclusion: Contact allergy to methyl 2-octynoate was frequently seen when patch testing with 2% in pet. However, active sensitization was also observed, when patch testing with concentrations of 1% and 2% methyl 2-octynoate. The patch test concentration should be below 1% in pet., but a safe concentration remains to be defined.