Solar dermatitis

We all enjoy sunbathing, and our cats often enjoy it too. But we know to use sunscreen to prevent sunburn and the risk of skin cancer – should we be worried about risks to our feline companions?

This disease is a skin problem caused by long term, repeated exposure to sunlight. It particularly affects white, relatively hairless skin, usually on a cat’s ears, but can also occur in other areas such as the eyelids, nose or mouth. White cats, or colored cats who have white patches on these areas, are most at risk.

Feline solar dermatitis is due to a reaction of the skin to ultraviolet (UVB) light. It starts as redness and loss of any hair over the affected region. This primary stage is mild and often ignored, but the damage done builds up over time until it progresses to scaling and crusting of the skin. These changes lead to more hair loss which, in turn, increases the area exposed to the sun and worsens the problem. To begin with the disease tends to improve in the winter, but over the next few summers it gets progressively worse and the skin may get very sore. The skin may become painful, and the cat will often scratch at it, causing more damage and inflammation. At this stage the disease can cause the ears to curl at the edges, or cause crusty areas on the nose, eyes or mouth.

It is usually possible to make a provisional diagnosis of the disease based on the history of the symptoms and examination of the affected areas. However, a number of other diseases (eg parasites, ringworm, skin tumors and diseases of the immune system) can look the same as feline solar dermatitis; your veterinarian may need to take a skin biopsy or perform other tests to rule these out and confirm the diagnosis.

To protect your cat, stop them going outdoors and sunbathing at open windows or doors during the sunniest part of the day. When the cat does go outside, a waterproof, total sun block should be applied to the white areas of the ears and nose. Some veterinarians have used special drugs (retinoids) to treat cases, though these are not widely available. Others recommend removal of the worst affected areas to prevent the progression of the disease to a form of skin cancer (see below). If these treatments are not successful, then more radical surgery may be required.

Yes, it can be. Feline solar dermatitis can progress over time, usually a number of years, into a type of skin cancer called squamous cell carcinoma (SCC). If SCC occurs on the ears it may be possible to treat this by amputation. If SCC occurs on the nose or mouth, surgery may be more difficult and it might not be possible to remove the tumor completely. Other forms of treatment, such as radiotherapy (a special kind of X-ray), can be used for areas where surgery is not possible although the chance of curing the disease is slim. Although SCC rarely spreads to distant tissues, in sites where surgery is not possible it can be difficult to treat successfully.