Photoallergic contact dermatitis due to combined UVB (4-methylbenzylidene camphor/octyl methoxycinnamate) and UVA (benzophenone-3/butyl methoxydibenzoylmethane) absorber sensitization

In a 71-year-old male Caucasian patient with persistent eczema on light-exposed skin, photocontact allergy was demonstrated to the UV filter substances 4-methylbenzylidene camphor (UVB), octyl methoxycinnamate (UVB), benzophenone-3 (UVA) and butyl methoxydibenzoylmethane (UVA) present in sunscreen products used by the patient over several years. A significantly reduced UVB sensitivity of 25 mJ/cm² in this patient (normal minimal erythema dose in our laboratory = 70-130 mJ/cm²) was considered an early indication of a persistent light reaction. Topical anti-inflammatory treatment over 2 weeks together with consequent application of a sunscreen containing Mexoryl® SX/titanium dioxide led to complete remission. Taking into account the widespread use of the above UV filter substances not only in sun protection products, but also in cosmetics such as antiaging lotions and day care products, the possible risk of allergy to these chemicals has to be taken seriously. The substitution of known photocontact sensitizers in UV filters by photostable compounds and detailed product information are the basis of preventive strategies.