Drug-induced photosensitivity

Author: Vanessa Ngan, Staff Writer, 2006.

What is drug induced photosensitivity?

Drug-induced photosensitivity occurs when certain photosensitising medications cause unexpected sunburn or dermatitis (a dry, bumpy or blistering rash) on sun-exposed skin (face, neck, arms, backs of hands and often lower legs and feet). The rash may or may not be itchy.

Medications can also cause onycholysis (nail plate lifting off the nail bed). This is known as photo-onycholysis.

What causes drug-induced photosensitivity?

Drug- and chemical-induced photosensitivity occurs when a drug or chemical agent combines with UV radiation to cause a phototoxic or photoallergic reaction. These agents are called photosensitisers and can be topical agents or medications that are taken orally. The following table lists the most common medications and topical agents causing photosensitivity.

Common photosensitising medications

Antibiotics

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Diuretics

Retinoids

Hypoglycaemics

Antipsychotics

PDT Pro-photosensitisers

Targeted therapies

Other drugs

Common photosensitising topical agents

Sunscreens

Fragrances

Miscellaneous

What are the clinical features of drug-induced photosensitivity?

The clinical features of drug-induced photosensitivity vary according to the photosensitising agent involved and the type of reaction it causes in the skin. The reaction can be phototoxic and/or photoallergic.

Phototoxic reactions result from direct damage to tissue caused by light activation of the photosensitising agent, whilst photoallergic reactions are a cell mediated immune response in which the antigen is the light-activated photosensitising agent.

Photoallergic reactions occur less commonly than phototoxic reactions and are mostly caused by photosensitising topical agents. Although some oral photosensitising medications can cause photoallergic reactions, most cause phototoxic reactions. A handful of medications can cause both phototoxic and photoallergic reactions.

The clinical features differ between phototoxic and photoallergic reactions.

Phototoxic reactions

Photoallergic reactions

What is the treatment for drug-induced photosensitivity?

The main goal of treatment is to identify the photosensitising agent and if possible to avoid it. In cases where medication is being taken to treat an existing condition and can not be discontinued, patients should be advised to follow sun protection strategies, including wearing sun protective clothing and using sunscreen.

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