A high index of suspicion is needed to diagnose cases of photosensitivity as the temporal relationship of a rash on exposed sites with sunlight exposure is not always obvious.
- Photosensitivity is a feature of a wide range of disorders, including the idiopathic photodermatoses, some metabolic disorders and a few rare genetic syndromes. It also occurs after exposure to certain drugs and other exogenous agents.
- A photosensitive reaction classically occurs on sun-exposed sites and spares those that are shaded or covered by clothing.
- A history of exposure to a photosensitising agent must be explored in all patients with photosensitivity.
- Referral to a dermatologist, or a photodermatology centre if available, for light testing and patch testing may be helpful in establishing the diagnosis.
- General treatment measures include avoidance of photosensitisers and sun protection.
- Specific treatment measures include oral corticosteroids, antihistamines, antimalarials, cyclosporin, azathioprine, thalidomide and light therapy.