Photoallergy Photopatch Test Photo Patch Photoallergic reaction, hypersensitivity initiated specific immune reaction substances generated activated visible light VL ultraviolet radiation UVA UVB infrared radiation IR mechanism generation/activation allergen hapten, mechanism specific immune reaction mechanisms photoallergic reactions classical allergy photoallergic reactions fitting to Gell & Coombs type I and IV allergic reactions Diagnosis photoallergic contact dermatitis modification of patch tests irradiation tested skin area UV. UVA (wavelength 320-400 nm) rare cases UVB (290-320 nm) initiation of allergic reaction. UVA dose photopatch testing is 5-10 J/cm2 1/2 of Minimal Erythema Dose (MED) determined individually tested person haptens tested applied double sets irradiated interpreting photopatch test results sets of haptens are compared bright side (patch tests irradiated with UV) dark side (not exposed to UV) positive result bright negative result dark photoallergy classic contact allergy Photoallergy Photopatch Test Photo Patch Photoallergic reaction, hypersensitivity initiated specific immune reaction substances generated activated visible light VL ultraviolet radiation UVA UVB infrared radiation IR mechanism generation/activation allergen hapten, mechanism specific immune reaction mechanisms photoallergic reactions classical allergy photoallergic reactions fitting to Gell & Coombs type I and IV allergic reactions Diagnosis photoallergic contact dermatitis modification of patch tests irradiation tested skin area UV. UVA (wavelength 320-400 nm) rare cases UVB (290-320 nm) initiation of allergic reaction. UVA dose photopatch testing is 5-10 J/cm2 1/2 of Minimal Erythema Dose (MED) determined individually tested person haptens tested applied double sets irradiated interpreting photopatch test results sets of haptens are compared bright side (patch tests irradiated with UV) dark side (not exposed to UV) positive result bright negative result dark photoallergy classic contact allergy Photoallergy Photopatch Test Photo Patch Photoallergic reaction, hypersensitivity initiated specific immune reaction substances generated activated visible light VL ultraviolet radiation UVA UVB infrared radiation IR mechanism generation/activation allergen hapten, mechanism specific immune reaction mechanisms photoallergic reactions classical allergy photoallergic reactions fitting to Gell & Coombs type I and IV allergic reactions Diagnosis photoallergic contact dermatitis modification of patch tests irradiation tested skin area UV. UVA (wavelength 320-400 nm) rare cases UVB (290-320 nm) initiation of allergic reaction. UVA dose photopatch testing is 5-10 J/cm2 1/2 of Minimal Erythema Dose (MED) determined individually tested person haptens tested applied double sets irradiated interpreting photopatch test results sets of haptens are compared bright side (patch tests irradiated with UV) dark side (not exposed to UV) positive result bright negative result dark photoallergy classic contact allergy

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Basic facts

Photoallergy is a relevant burden to public health, and an exciting scientific challenge. As many as 5% of the general population have experienced episodes of photodermatoses (light-induced skin diseases, not to be confused with sunburn). Among these patients, 8% are diagnosed with photoallergic contact dermatitis. These figures have been confirmed in both European (Neumann et al. 2000) and American (Fotiades et al. 1995) populations.

The most frequent photosensitizers are substances abundant in our close surroundings: preservatives, perfumes and cosmetics, systemic and topical drugs. Paradoxically, also sunscreens are frequent causes of photocontact allergic dermatitis.

Photopatch testing is the gold standard in the diagnosis of photoallergic contact dermatitis. Therefore, every dermatologist and allergist should be acquainted with this method.

Photoallergy

Photoallergic reaction is a hypersensitivity reaction initiated by specific immune reaction to substances generated or activated by visible light (VL), ultraviolet radiation (UVA, more rarely UVB), and least frequently by infrared radiation (IR). It seems that the prefix "photo" seem to refer to the mechanisms of generation/activation of the allergen or hapten, rather than some exceptional mechanism of specific immune response. The mechanisms of photoallergic reactions seem identical with those of "classic" allergy. Until now, photoallergic reactions fitting to Gell & Coombs type I and IV allergic reactions have been well documented (Table 1).

Table 1. Types of allergic reactions and respective photoallergies
Type Description Respective photodermatosis Postulated role of irradiation Spectrum
I Immediate hypersensitivity, IgE-mediated Solar urticaria Initiation of photochemical reactions that result in generation of allergens from endogenous substances or xenobiotics UVA, VL, UVB, IR
II Cytotoxic reactions ? - -
III Immune complexes ? - -
IV Delayed hypersensitivity (contact allergy) Photoallergic contact dermatitis Initiation of photochemical reactions that result in generation of haptens from endogenous substances or xenobiotics; Initiation of coupling of haptens with carrier proteins to form full allergenic molecule UVA (rarely UVB)

Spiewak R. Photoallergic diseases - diagnosis and treatment. Alergol Immunol 2008; 5 (3-4): 101-105.

Photopatch testing

Diagnosis of photoallergic contact dermatitis requires respective modification of patch tests, i.e. irradiation of tested skin area with UV. Typically, UVA (wavelength 320-400 nm) is used; in rare cases UVB (290-320 nm) is necessary for the initiation of allergic reaction. The UVA dose used at photopatch testing is 5-10 J/cm2 or, alternatively, 1/2 of Minimal Erythema Dose (MED) determined individually for the tested person [53]. The haptens tested are applied in double sets, with only one being irradiated. While interpreting photopatch test results, both sets of haptens are compared: the "bright" side (patch tests irradiated with UV) with "dark" side (not exposed to UV). A positive result on the "bright" side with a negative result on the "dark" side suggests photoallergy, equal responses on both sides - "classic" contact allergy.

Spiewak R. Patch testing for contact allergy and allergic contact dermatitis. Open Allergy J 2008; 1: 42-51.

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European Society of Contact Dermatitis, ESCD, Institute of Dermatology, instytut dermatologii, congress, Derk P. Bruynzeel, James Ferguson, Alastair Kerr, Cezary Kowalewski, Percy Lehmann, Joanna Narbutt, Radoslaw Spiewak, Hanna Wolska, meeting, symposium, course, photobiology photodamage of the skin, skin barrier and the UV, sunscreens and skin protection, common and rare photodermatoses, photoallergy, phototherapy, diagnosis and treatment of photodermatoses, quality of life in photodermatoses, patient education  and public health issues related to photodermatoses, photopatch test, patch test, photoallergy, photocontact dermatitis, photo contact dermatitis, contact allergy, sun allergy, dermatology, allergology, skin diseases, allergy, conference, course, workshop, Krakow, Cracow, Cracovie, Poland, Europe, EU, meeting, course, conference, 18 september 2009, 19 september 2009 Krakow (Cracow)

European Society of Contact Dermatitis, ESCD, Institute of Dermatology, instytut dermatologii, congress, Derk P. Bruynzeel, James Ferguson, Alastair Kerr, Cezary Kowalewski, Percy Lehmann, Joanna Narbutt, Radoslaw Spiewak, Hanna Wolska, meeting, symposium, course, photobiology photodamage of the skin, skin barrier and the UV, sunscreens and skin protection, common and rare photodermatoses, photoallergy, phototherapy, diagnosis and treatment of photodermatoses, quality of life in photodermatoses, patient education  and public health issues related to photodermatoses, photopatch test, patch test, photoallergy, photocontact dermatitis, photo contact dermatitis, contact allergy, sun allergy, dermatology, allergology, skin diseases, allergy, conference, course, workshop, Krakow, Cracow, Cracovie, Poland, Europe, EU, meeting, course, conference, 18 september 2009, 19 september 2009 Krakow (Cracow)

European Society of Contact Dermatitis, ESCD, Institute of Dermatology, instytut dermatologii, congress, Derk P. Bruynzeel, James Ferguson, Alastair Kerr, Cezary Kowalewski, Percy Lehmann, Joanna Narbutt, Radoslaw Spiewak, Hanna Wolska, meeting, symposium, course, photobiology photodamage of the skin, skin barrier and the UV, sunscreens and skin protection, common and rare photodermatoses, photoallergy, phototherapy, diagnosis and treatment of photodermatoses, quality of life in photodermatoses, patient education  and public health issues related to photodermatoses, photopatch test, patch test, photoallergy, photocontact dermatitis, photo contact dermatitis, contact allergy, sun allergy, dermatology, allergology, skin diseases, allergy, conference, course, workshop, Krakow, Cracow, Cracovie, Poland, Europe, EU, meeting, course, conference, 18 september 2009, 19 september 2009 Krakow (Cracow)

European Society of Contact Dermatitis

ESCD - GERDA Strasbourg 2010

Institute of Dermatology, Krakow

dermatoses.eu

© Radoslaw Spiewak (contact).
This page is part of the website photopatch.eu
Document created: 11 September 2008, last updated: 6 September 2009.