Alopecia

Alopecia: A pathological skin condition resulting in the loss of hair outside the moulting season, with the falling out in patches. Avoid home remedies (especially with an alcohol base) and take the cat to the vet immediately.

What is alopecia?

Alopecia is defined as abnormal hair loss which can be anything from a generalised diffuse thinning of the coat to localised bald patches. Before we consider genuine alopecia we should be aware of conditions which are perfectly normal in the cat but which occasionally concern owners. Most cats have slightly sparse hair in the area between their ears and their eyes but some individuals have quite exaggerated “tramlines”. These are particularly noticeable in the oriental breeds such as the Siamese. The other normally sparse area is around the nipples which run in two rows on the underside of the cat between front and back legs (this may seem like stating the obvious but it’s surprising how many people don’t realise cats have nipples too!).

What causes genuine alopecia?

Self inflicted hair loss is by far and away the most common cause of alopecia in the adult cat. Cats have tongues like rasps and if they have an itchy skin they tend to groom excessively. The spikes on their tongues either rip the hair out by its roots or snap the hair part way down its shaft. The bald area may have an obvious stubbly feel but sometimes this isn’t immediately apparent on touch. Some cats are very secretive about their grooming and will only do it out of sight of their owners. It can be difficult to convince ourselves that the cat’s tongue can be the cause of the hair loss but the presence of fractured hair shafts under the microscope provides undeniable evidence that self-inflicted damage is present. The most common reason for self-inflicted hair loss is a parasite infestation. Parasite related alopecia in the dog is often the result of a mange mite infestation but this is rare in the cat. Nevertheless we have to consider this if a cat continues to have an ongoing skin problem. The Demodex mite tends to cause itching and scabbing round the neck but may appear as a symmetrical hair loss. The mite can be identified when skin scrapings are looked at under the microscope. A diagnosis of demodex mite infestation should always lead to an investigation for underlying disorders which may cause the body to be unable to defend itself properly against the mite. Diabetes, Feline Leukaemia Virus (FeLV) infection and Feline Immunodeficiency Virus (FIV) infection can all predispose to demodex mite problems.

Our old friend, the flea, is the most commonly encountered cat parasite but rarely causes significant itches or alopecia in normal cats. An allergic or hypersensitive individual is a different matter. The immune system protects the body against infection but an allergy is an exaggerated, aberrant immune response to a normally harmless substance. Exactly why allergies exist is unclear but there are probably genetic and/or environmental factors at play. Allergic skin disease can crop up in a variety of forms. Cats can develop localised crusty sores, plaques of inflammatory tissue or multiple pinpoint scabs all over the body. One of the more characteristic presentations of an allergic cat is the development of baldness on the underside of the tummy and down the back legs.

Cat allergies can be very frustrating conditions because we usually have to work through a process of elimination which can drag on for weeks if not months. Sometimes we never manage to accurately identify the trigger and if the cat is tearing lumps out of itself we have to step in with medication to make it more comfortable. The most powerful drugs are corticosteroids which help to dampen down the immune response. These are very useful in the short term control of itches and alopecia but although the cat is more resistant than other species to potential side effects, they’re not drugs we like to see our patients on for months or years. Antihistamines have fewer long-term side effects but their use can be a bit hit and miss. We’re now finding that a dietary supplement of essential fatty acids (the cat equivalent of evening primrose oil) can be very useful in controlling itches because the oils possess a natural anti-inflammatory effect.

Skin infections are frequently involved in localised bald patches. If, during a cat fight, an opponent’s tooth or claw pierces the skin, a bacterial infection can be introduced. An abscess brews beneath the surface and after a few days bursts and discharges pus. The first the owner may be aware of is a large bald patch surrounding a central sore. Ringworm is caused by a group of highly specialised fungi (not worms) which live on the skin surface. Healthy cats are commonly exposed to the ringworm fungi, either from contact with an infected individual or from a contaminated environment. A normal, intact skin is a relatively impervious barrier to ringworm but if the skin is damaged - if a cat is scratched or has a pre-existing skin disease- the fungal infection can take a hold. In kittens, the lesions typically appear as one or more patchy bald areas usually around the face, ears and front legs. The skin is often unmarked but rashes or scabs may be seen. Ringworm infection is usually not itchy in affected cats. If you look closely, hairs in the affected area will be broken off or frayed. In adult cats, the condition may be more widespread. Less commonly ringworm infection may have a very similar appearance to that of allergic skin disease. Sometimes ringworm will cause a recurring “acne” on the chin or eyelid infections. Microscopy of hair pluckings can help determine if there is ringworm infection. We can also examine the cat with a Wood’s lamp which causes hair affected with ringworm fungus to fluoresce under ultraviolet light.

Are there any other causes of alopecia?

Although we generally describe alopecia as a hair loss it can be as a result of a failure of hair production. The most dramatic example of this is in the Sphinx or Canadian Hairless breed of cat which has a congenital baldness. What essentially started out as a genetic quirk or mutation was thought of as a desirable feature and developed into a breed. A similar condition occurs every now and again within the Devon and Cornish Rex breeds. We can’t offer any treatment for congenital alopecia.

In the past, some allergies were misdiagnosed as hormone imbalances. In other species, hormone deficiencies can cause symmetrical hair loss. Many allergic cats have such a pattern, particularly those who develop the bald undercarriage. We assumed that because these cases responded to hormone treatment they must be hormone deficiencies but we’ve since discovered that the body metabolises the hormone supplement into a substance with anti-inflammatory activity, hence the improvement in the condition. An underactive thyroid gland is a relatively common cause of symmetrical hair loss in the dog but spontaneously occurring underactive thyroid disorders are extremely rare in the cat. A sluggish thyroid problem may be encountered after a cat has had surgery on its thyroid gland. We’re seeing more and more old cats affected by overactive thyroids and these individuals often undergo thyroid surgery. Sometime it’s unavoidable that in the process of surgery to correct this condition our patient is tipped the other way and develops an underactive thyroid. In the dog, the sides of the body often have sparse hair but with cats for some reason it’s their ears that go bald.

Another hormonal condition which can induce alopecia is an overproduction of the body’s corticosteroid hormone. Affected cats develop symmetrical baldness over the body usually accompanied by blackheads and a characteristic thin skin.

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