Photosensitive dermatitis

Chapter 17 Photosensitive dermatitis






2. What is the difference between a phototoxic reaction and a photoallergic reaction?
A phototoxic reaction (Fig. 17-1) is an exaggerated “sunburn” reaction where skin cells are damaged directly by electromagnetic radiation through the production of free radicals, toxic metabolites, heat, or by direct damage to DNA, augmented by external chemicals. It may occur within minutes to hours of exposure, though it may also be delayed for a day or two. A phototoxic reaction can be produced in anyone given a high enough dose of ultraviolet (UV) light and a phototoxic chemical. It can happen on first-time exposure without a need for sensitization.

A photoallergic reaction only occurs in sensitized individuals when electromagnetic radiation (usually ultraviolet light, but sometimes visible light) interact with an endogenous (Fig. 17-2A) or exogenous (Fig. 17-2B) chemical, converting it to an allergen that the person’s immune system recognizes as an allergen (requires more than one exposure). Photoallergic reactions typically occur 1 to 3 days after exposure (with the exception of solar urticaria, which is immediate). Phototoxic reactions tend to be well demarcated in the areas of exposure. Photoallergic reactions are also photodistributed, but often have extension of the cutaneous reaction onto covered areas or even distant sites in an autoeczematous type of eruption. Sometimes chemicals may produce both a phototoxic and photoallergic phenomenon.




5. Name some of the most common systemic phototoxic and photoallergic agents and their action spectrums.
As in the case of the topical agents, the action spectrum for almost all systemic phototoxic and photoallergic reactions is UVA, rarely UVB and visible light. Some of the most common systemic agents are listed in Table 17-2.

Table 17-1. Topical Agents Causing Phototoxic and Photoallergic Reactions









PHOTOTOXIC CHEMICALS PHOTOALLERGIC CHEMICALS
Benzocaine
Benzoyl peroxide (UVB)
Coal tar
Erythromycin
Halogenated salicylanilides
Hydrocortisone
Ketoprofen
Porphyrins (visible light and UVB)
Psoralens
Sunscreens: oxybenzone, benzophenone, etc.
Fragrances: methylcoumarin, musk ambrette, sandalwood oil
NSAIDs
Oxicams: ampiroxicam, droxicam, meloxicam, piroxicam, tenoxicam
Prioprionic acid derivatives: benzophenone, dexketoprofen, ketoprofen, piketoprofen, suprofen (UVA and UVB), tiaprofenic acid, diclofenac
Antimicrobials: bithionol, chlorhexadine, fenticlor, hexachlorophene
Phenothiazines: chlorpromazine, promethazine
Miscellaneous
Acyclovir
Dibucaine
Halogenated salicylanilides (UVA and UVB)
Hydrocortisone

Table 17-2. Systemic Agents Causing Phototoxic and Photoallergic Reactions









PHOTOTOXIC PHOTOALLERGIC
Antimicrobials
Tetracyclines: demeclocycline, dimethylchlorotetracycline, doxycycline, lymecycline, minocycline, tetracycline
Quinolones: ciprofloxacin, enoxacin, fleroxacin, levofloxacin, lomefloxacin (UVA and UVB), nalidixic acid, pefloxacin, sparfloxacin
Griseofulvin
Voriconazole
Sulfur-containing medications: bumetanide, furosemide, hydrochlorothiazide, sulfonamides (UVB), sulfonylureas
NSAIDs: proprionic acid derivatives: benzophenone, carprofen, ketoprofen, nabumetone, naproxen, suprofen (UVA and UVB), tiaprofenic acid
Antimalarials: chloroquine unknown, hydroxychloroquine (UVB), quinidine
Miscellaneous: amiodarone, atorvastatin (UVB), calcium-channel blockers, chlorpromazine, prochlorperazine, porphyrins (UVB and visible), psoralens, retinoids (UVA and UVB), St. John’s wart (hypericin)
NSAIDs: piroxicam, celecoxib, ketoprofen
Sulfur-containing medications: hydrochlorothiazide, sulfacetamide (UVB), sulfadiazine (UVB), sulfapyradine (UVB), sulfonamides (UVB), sulfonylureas
Antimalarials: chloroquine unknown, hydroxychloroquine (UVB), quinidine, quinine
Antimicrobials: chloroamphenicol unknown, enoxacin, lomefloxacin (UVA and UVB), sulfonamides
Griseolfulvin
Phenothiazines: chlorpromazine, dioxopromethazine, perphenazine, thioridazine
Miscellaneous: amantadine, dapsone unknown, diphenhydramine (UVB), flutamide (UVA and UVB), pilocarpine, pyridoxine, ranitidine

Stein, KR, Scheinfeld, NS: Drug-induced photoallergic and phototoxic reactions, Expert Opin Drug Saf 6:431–443, 2007.



Apr 26, 2016 | Posted by in Dermatology | Comments Off on Photosensitive dermatitis

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