Check-up: Photosensitivity

Today, I developed a severe rash on my neck and upper chest after being out in the sun for just a few minutes.

Being dark skinned I don’t usually burn, but I’ve been left with a very red, sensitive sunburnt patch, with small, itchy hives.

A friend suggested the reaction could be related to some medication I’ve just started on.

Photosensitivity is an abnormal skin reaction that develops after exposure to ultraviolet (UV) light, either from the sun or from artificial light.

The reaction can be either phototoxic or photoallergic, with the former accounting for 95 per cent of all cases of photosensitivity. It occurs as a result of ingesting certain medications followed by exposure to UV light.

The degree and severity of the reaction is directly linked to the dose of medicine and the amounts of exposure to UV light.

A wide range of drugs can cause photosensitivity. These include non steroidal anti-inflammatory drugs and certain types of treatments for rheumatoid arthritis and lupus.

Antibiotics, tricyclic antidepressants and anti-hypertensive drugs can also cause phototoxic skin reactions.

The reaction typically occurs within 24 hours of taking the drug and being exposed to the sun.

The most common symptoms include the appearance of areas of severe redness on skin exposed to light.

Where the offending drug is taken in high doses, swelling and blisters can occur and urticaria (hives) may also develop. Symptoms usually resolve within two to seven days of stopping the medication.

A photoallergic reaction is caused by a topical ointment (applied directly to the skin) reacting with UV radiation. The reaction may occur in areas not exposed to the sun, and is likely to happen with even a small amount of the irritating topical agent.

Should I stop taking the antibiotics?

You should talk to your doctor first before stopping the drug. If he or she is of the opinion that antibiotics are the cause of your photosensitivity, you will just need to avoid sun exposure while taking them.

Minimise your exposure to the sun in terms of duration and coverage. Wear light-coloured clothing and cover up with long-sleeved shirts, long trousers or skirts.

Apply sunscreen, factor 15 or higher, and preferably one containing physical blockers such as zinc oxide and/or titanium dioxide, recommended as a preventative measure against sun sensitivity.

And don’t forget to wear sunglasses and a wide-brimmed hat to ensure maximum protection.

mkerr@irishtimes.com