Photoepicutaneous tests: a series of 37 Brazilian patients

Photoepicutaneous tests or photopatch tests (PPT) are indicated for the diagnosis of allergic contact photodermatitis (ACPD), a delayed hypersensitivity reaction that occurs when a photoallergen is applied to the skin that is subsequently exposed to ultraviolet (UV) and/or visible radiation. Its incidence is unknown; it is estimated to range from 2% to 10% of patients referred for investigation of photodermatoses. Patients treated at the Contact Dermatitis Outpatient Clinic, Dermatology Annex, Hospital das Clínicas, UFMG between 2007 and 2019, with diagnostic suspicion of photodermatosis due to eczematous lesions in exposed areas, exacerbated after sun exposure, were selected to undergo PPT for diagnostic purposes after the epicutaneous test with the standard Brazilian panel revealed no clinical relevance. Allergens from FDA-Allergenic, Rio de Janeiro and Chemotechnique Diagnostics, Sweden (Table 1) were used in Finn Chambers with Scanpor (Smartpractice, United States) or Allergochambers (Neoflex, São Paulo) applied in duplicate on the skin of the back. The set of allergens tested was chosen based on the literature and availability in this service. The allergen panel was removed after 48 h, read, and covered with surgical dressing and aluminum foil. As no patient presented a minimal erythematous dose less than 10 J/cm of UVA, the other set of allergens was irradiated with 10 J, followed by immediate reading and subsequent occlusion. New readings were performed 48 h later, following the International Contact Dermatitis Research Group criteria. If only the irradiated side showed a positive reaction, the diagnosis of photoallergic contact reaction was made. If both sides had positive reactions, but there was a stronger reaction on the irradiated side, the diagnosis was photodermatitis and allergic contact dermatitis; if the reactions were equal on both sides, the diagnosis was allergic contact dermatitis (ACD). Among 1712 patients undergoing epicutaneous tests, 37 (2.2%) were selected: 19 men (51.4%) and 18 women (48.6%), aged 30--80 years, 22 (59.4%) of phototypes II and III, seven (19%) of IV and V, and eight (21.6%) of VI. Six patients (16.2%) had a history of atopy, 15 (40.5%) used sunscreens, 31 (84%) had varied occupations, four (11%) were bricklayers, and two (5.4%) were farmers. The time of evolution of the lesions ranged from five months to 20 years and the most affected sites were exposed areas, predominantly the face (33%--89%), upper limbs (25%--67%), and neck (24%--65%). Three patients (8%) had disseminated lesions. Prior patch test indicated Kathon and quaternium-15 reaction in one patient, formaldehyde in one, and potassium bichromate in two; one patient reacted to nickel, thimerosal, and hydro-