Solar dermatitis

Solar dermatitis, or actinic dermatitis, is a skin disease caused by exposure to the sun. It’s seen mostly in cats with white, non-pigmented areas of skin. The ear flaps, nose and lower eyelids are the most commonly affected areas. Left untreated, some cases progress to a malignant tumour, or squamous cell carcinoma (SCC).

If you have a cat with skin predisposed to solar dermatitis, you can minimise the risks by keeping the animal out of sunlight, particularly between the hours of 9am and 4pm on sunny days. An animal specific sun block cream (available at the hospital) may also be used on affected areas, although most cats will rapidly groom or lick this off.

Clinical signs:

In the early stages, the skin may look pink and scaly with some degree of hair loss. As the condition progresses the affected area becomes crusted and eroded. The cat is often irritated by the lesions and, if the ears are affected, it may shake its head and cause bleeding from the ear tips.

How is solar dermatitis diagnosed?

Initial diagnosis is by physical signs. If we are concerned the condition may be progressing to a squamous cell carcinoma, we will take a biopsy from the affected area, which will be microscopically examined to see if malignant cells are present.

Treatment protocols:

For cats with an SCC, surgical removal of the affected area and a wide surrounding margin is the most effective treatment. This is usually straightforward. If the ears are affected complete removal of the ear flaps may be necessary. This has no detrimental affect on the cat and the final appearance is often quite acceptable. Surgery is more difficult when the nose or eyelids are affected. Where it is not possible to remove all the diseased tissue, additional forms of therapy may be needed such as radiotherapy. In advanced cases, with nose involvement, removal of the nose is possible as a last resort.

The prognosis following is usually good, especially when it is the ears that are involved, and particularly if the disease if discovered early. If all the diseased tissue is not adequately removed, the tumour will recur at the operation site. This can be a problem if the nose or the eyelids are affected and is the reason additional therapies are often used in these cases.

This type of tumour doesn’t spread very rapidly to other parts of the body so removal and treatment of the site of SCC’s often produces complete remission, as long as the entire tumour is removed.