What are photoallergic reactions?

A photoallergic reaction is where drugs or other chemicals are converted by sunlight to a chemical which the immune system then attacks. The newly made chemical is treated by the body as an allergen. Between 24 and 72 hours after exposure to sunlight, you may notice an itchier area of skin. This reaction is not restricted to those parts of the body exposed to sunlight – it can affect the entire body. You might also notice a rash.

Drugs and chemicals which can commonly cause these reactions include:

• Thiazides.
• Enalapril, a type of ACE-inhibitor, which can lower blood pressure by interfering with a chemical reaction in the body.
• Phenothiazines.
• Hydroxychloroquinine (a drug used to treat malaria)

Photosensitivity Guide Index:

• What is photosensitivity?
• What are some photosensitive dermatoses caused by drugs or other chemicals?
• What are phototoxic reactions?
• What are photoallergic reactions?
• What is photocontact dermatitis?
• What are genetic and metabolic metabolic photosensitive dermatoses?
• What is pellagra?
• Who gets pellagra?
• What are some signs and symptoms of pellagra?
• What are porphyrias?
• What are acute porphyrias?
• What are cutaneous porphyrias?
• What is xeroderma pigmentosum?
• What is Bloom syndrome?
• What is Cockayne syndrome?

• What are photoaggravated dermatoses?
• What is atopic eczema?
• What is psoriasis?
• What is lichen planus?
• What is lupus erythematosus?
• What is dermatomyositis?
• What is actinic folliculitis?
• What is disseminated superficial actinic porokeratosis?
• What are acquired idiopathic photosensitive dermatoses?
• What is polymorphic light eruption?
• What is chronic actinic dermatitis?
• What is solar urticaria?
• What is actinic prurigo?
• What is hydroa vacciniforme?
• What is juvenile spring eruption?