Contact and photocontact sensitization in chronic actinic dermatitis: sesquiterpene lactone mix is an important allergen

Eighty-nine patients with chronic actinic dermatitis (CAD) were retrospectively studied: 69 (78%) male and 20 (22%) female, with mean ages of 66 and 64 years, respectively; nine (10%) were dark skinned. Eight (9%) were abnormally sensitive to UVB wavelengths alone, 74 (83%) to UVB and UVA, and seven (8%) to UVB, UVA and visible radiation. Eighty-six patients were patch tested to an extended standard European series of contact allergens, including in 80 cases a 0.1% mix of three sesquiterpene lactones, and photopatch tested to a standard photopatch series. Sixty-four of these 86 patients (74%) had positive patch or photopatch tests; 36% (29 of 80) were sensitive to the sesquiterpene lactone mix, 21% (18 of 86) to fragrance compounds, 20% (17 of 86) to colophony, and 14% (12 of 86) to rubber chemicals. Ten (12%) had positive photopatch tests; five (6%) to musk ambrette, six (7%) to sunscreens and one to both. Fourteen of the eighty-nine patients with CAD (16%) had preceding endogenous eczema. In 18 of 86 patients (21%), CAD occurred alone, with neither detectable contact nor photocontact allergy, nor a preceding history of endogenous eczema. This study confirms the association between Compositae (sesquiterpene lactone) dermatitis and CAD.