Phototoxic, which can occur in all individuals and is essentially an exaggerated sunburn response (erythema, edema, vesicles, etc.). Phototoxic drug reactions are more frequent than photoallergic drug sensitivity.
Causes of Phototoxic Drug Induced Photosensitivity
Formation of toxic photoproducts such as free radicals or reactive oxygen species such as singlet oxygen. The principal sites of damage are nuclear DNA or cell membranes (plasma, lysosomal, mitochondrial). The action spectrum is UVA.
Symptoms of Phototoxic Drug Induced Photosensitivity
People with fair complexions; red, blonde or light brown hair; blue or green eyes; and who generally sunburn easily and do not tan are most at risk.
A phototoxic reaction usually has a rapid onset (within several hours after exposure to ultraviolet radiation) and presents as an exaggerated or intensified sunburn with erythema (redness), pain and prickling or burning. Blistering, desquamation (peeling) and hyperpigmentation (abnormally increased coloration of the skin) may occur in severe
Diagnosis
History of exposure to drugs is most important as well as the types of morphologic changes in the skin characteristic of phototoxic drug eruptions: confluent erythema, edema, vesicles, bullae.
Treatment
- Topical corticosteroids and cool compresses may alleviate the condition.
- The use of systemic corticosteroids should be reserved for the most severe cases.
- If sunscreens are not the cause of the photosensitivity, they should be used liberally.
- Sunscreens that contain avobenzone (Parsol 1789), titanium dioxide, and zinc oxide are more effective in blocking out UV-A radiation than sunscreens that contain other ingredients.
References