Photoallergic contact dermatitis

Background: Photoallergic contact dermatitis (PACD) presents in patients after certain exogenous agents come into contact with the skin in the presence of ultraviolet and/or visible light. The best method currently available for investigating PACD is photopatch testing. However, photopatch testing as an investigation is under‐used by clinicians, and therefore PACD may go undetected in many patients. Purpose: To highlight the importance of PACD and photopatch testing when investigating patients with a photo‐exposed site dermatosis. Method: A comprehensive review of the available literature relating to PACD and photopatch testing. Results: Experimental evidence suggests that PACD is a delayed type hypersensitivity reaction. Various agents have been historically shown to cause PACD, but currently the most common photosensitizers are sunscreens and topical non‐steroidal anti‐inflammatory drugs. Photopatch testing has in the past been subject to differing methodologies; however, a European consensus methodology now exists and should allow a greater comparison of results across centres. As chemical, pharmaceutical, and cosmetic industries produce new agents, photopatch testing of such agents in humans before release in the marketplace may prevent widespread contact with potent photosensitizers. It will also be important for ongoing multi‐centre studies of existing agents to be conducted in order to keep the photopatch test batteries used by clinicians investigating PACD up to date.     

Photoallergic contact dermatitis due to mineral oil

A 39-year-old metal polishing mechanic had had an acute-on-chronic eczematous eruption on sun-exposed skin for 2 years. It improved in winter. He had been using an insoluble oil, CRT 20, as a cutting oil for 20 years. The cutting oil itself and mineral oil, which was one of its ingredients, showed positive reactions on photopatch testing. The difference action spectrum with or without mineral oil application, assessed at 48 h, ranged from 300 to 350 nm, with a peak at 320 nm. This is the 1st report of photoallergic contact dermatitis due to mineral oil.     

Photoallergic contact dermatitis to Heracleum giganteum

Heracleum plants occur in numerous species worldwide and may cause phototoxic reactions due to its content of various furocoumarins. In this case report, a widespread photoallergic contact dermatitis after exposure to Heracleum giganteum (giant bear claw) is described. A photopatch test with extracts from the stem, leaves and seeds of the giant bear claw revealed a positive papulovesicular reaction that already appeared at 24 h and peaked at 72 h after irradiation with 5 J/cm(2) UVA. The unirradiated controls remained negative. We conclude that in rare cases Heracleum plants may cause severe photoallergic reactions that can be verified by photopatch testing.     

Photoallergic contact dermatitis from topical diclofenac in Solaraze gel

Solaraze gel (Shire Deutschland GmbH & Co. KG, Cologne, Germany) containing 3% diclofenac has been licensed in 2001 as a topical treatment for actinic keratoses. It is commonly used in dermatological practice. Undesirable effects are believed to be rare but include pruritus, paresthesia and application-site reactions (dry skin, rash, erythema, contact dermatitis and vesicobullous eruptions). Recently, a few cases of contact dermatitis due to three different allergens including diclofenac have been reported (1,2).     

Photoallergic contact dermatitis from ketoprofen in southern Sweden

The non-steroidal anti-inflammatory drug ketoprofen is widely used for topical treatment. In Sweden, ketoprofen has been available for topical application since 1995. Photoallergic contact dermatitis from ketoprofen-containing topical preparations usually includes severe eczematous reactions. Ketoprofen is derived from propionic acid, and it is also a substituted benzophenone and therefore structurally similar to fenofibrate and sunscreen agents based on benzophenones. During the last 2 years, 35 patients have been refereed to our department with suspected photoallergic or allergic reactions after having used ketoprofen-containing gels. Photopatch testing with the photopatch standard series, the ketoprofen-containing gels and their ingredients, fenofibrate, benzophenone-3, benzophenone-10 and benzophenone-4, was performed. Photoallergic reactions to ketoprofen were noted in 35 patients and a simultaneous contact allergy to ketoprofen in 2 patients. Simultaneous photoallergy to fentichlor, tetrachlorosalicylanilide and fenofibrate was registered in 74%, 40% and 73% of the patients, respectively.     

Photoallergic contact dermatitis from benzydamine presenting mainly as lip dermatitis

Background: Benzydamine, a non‐steroidal anti‐inflammatory drug (NSAID) in use for more than four decades, has been reported to cause photosensitivity. Objectives: To study the results of photopatch testing to benzydamine and the clinical features of the dermatitis during a 3‐year period (2006–2008). Patients and methods: During this period, 74 patients with photodermatoses were photopatch tested with an extended baseline series of allergens including benzydamine and in suspicious cases, with drugs that contain it. Test sites were irradiated on D2 with 5 J/cm² and readings were performed on D2 and D4. Results: Ten patients (six females/four males), aged 21–84 years (mean 64.9) had a positive photopatch test to benzydamine [1–5% petrolatum (pet.) from Bial‐Aristegui^®] and to drugs that contain it (Tantum verde^® oral solution and Momen^® gel). Nine patients had lower lip cheilitis and one lichenified eczema on photo‐exposed sites. Conclusion: Photosensitivity from both topical and systemic benzydamine has been occasionally described, mainly in southern Spain. Despite its widespread use and its known photosensitizing capacity, photoallergic contact dermatitis from benzydamine is probably underdiagnosed as the clinical presentation of mainly the lip and chin is not typical of photoallergic contact dermatitis and benzydamine is not part of most photoallergen series.