Chronic Actinic Dermatitis

Written by Dr James Ferguson, consultant dermatologist

Chronic actinic dermatitis (CAD), sometimes known as photosensitivity dermatitis/actinic reticuloid syndrome (PD/AR), is a condition in which the skin becomes inflamed, particularly in areas that have been exposed to sunlight or artificial light.In addition, the majority of CAD patients have allergies to some substances that come into contact with their skin, particularly various flowers, woods, perfumes, sunscreens and rubber compounds.

The condition particularly affects men over the age of 50, but also arises in women and is increasingly found in young male or female patients with atopic eczema.

This is not a life-threatening condition, but it does require significant changes in lifestyle to avoid contact allergies and intense sources of light.

Although the cause is not known, it is suspected that the body's defence system over-reacts to substances within the skin that are made 'allergic' by ultraviolet and visible light.

Many patients are spontaneously cured, but this may take several years and in the intervening period, patients have to learn to live with the condition, managing it by minimising their exposure to ultraviolet and visible light as well as chemicals.

Because the photosensitivity involves non-sunburn wavelengths of light (longwave ultraviolet and visible wavelengths), patients can develop the problem even on cloudy days, and windows and clothing offer no protection (unless the clothing totally blocks the light out). As a result, it is not always obvious that light is the source of the problem, and doctors may have difficulty in diagnosing the condition. One helpful tip is to check the parts of the patient's skin that are not exposed to light, such as under a watchstrap, to see if the condition is present there.

Phototesting using specialised equipment is possible in some university dermatology centres. Phototesting consists of having areas of skin exposed to known amounts of light of specific wavelengths and then looking at the reactions with comparison to the average population response. This procedure is painless and can be repeated to assess improvement. Patch testing, another way of confirming CAD diagnosis, is conducted by most dermatologists. A range of chemicals is applied to the skin and left for two days. The skin is then assessed for reactions.

Treating CAD involves the following:
Avoid direct exposure to sunlight between the hours of 11am and 3pm, with outdoor activities being limited to the earlier and later hours of the day.
Wear appropriate clothing along with a wide-brimmed hat and a neckerchief to protect the back of the neck.
Avoid direct exposure to ultraviolet sources at home or at work (such as fluorescent and metal halide lights).
Use protective plastic film on home and car windows. This can be of the clear, sticky-backed variety and is not noticeable when in place.
Avoid contact allergies.
Use a broad-spectrum sunscreen (seek medical advice).
Topical (ie, applied to the surface of the body) steroid creams/ointments are useful when a flare has occurred. Potent varieties should be used only in the short term.
Occasionally, treatment with tablets, which are prescribed by your dermatologist. Like all other potent therapies, the benefits have to be weighed up against the risks and it is useful to discuss this with your doctor.

There is good evidence that this condition will completely clear in a significant number of patients without the need for therapy. This may, however, take many years and it is important to discuss this with your doctor.