Hair loss (alopecia)

Hair loss (alopecia) can occur when hair fails to grow at a normal rate or when hair is lost more quickly than it can grow back. It can result from a variety of medical conditions, including skin infections, hormonal diseases, and infestations with parasites. Many causes of hair loss are treatable and if the hair follicle has not been permanently damaged or destroyed, the hair will grow back over time.

Alopecia is the medical term used to describe hair loss. It can occur when hair fails to grow at a normal rate, or when hair is lost more quickly than it can grow back. Overgrooming alopecia is very common in cats, and this is different to spontaneous hair loss. Alopecia should not be confused with increased shedding (even year-round shedding in some pets) which is a normal process. Shedding should only be a cause for concern if it is heavy enough to create areas of thinning hair or baldness consistent with alopecia.

Hair growth occurs in a cycle and depends on a healthy, functioning hair follicle. Once a hair grows, it is maintained within a hair follicle until a new hair grows to replace it. When this occurs, the old hair is shed, and the new hair is held within the hair follicle until it is shed and replaced in its turn. If hair follicles are damaged, destroyed, or affected by inflammation or infection, hair loss can occur, and hair regrowth can be hindered. When this happens over a large enough area, alopecia or baldness can be observed. We also see alopecia if a cat is overgrooming, causing damage to their fur and thinning of the coat.

Common causes of alopecia in cats include:

• Skin trauma: for example, burns or rubbing from a poorly fitting collar.
• Congenital or hereditary: abnormal development or lack of hair follicles. Some breeds like the Sphynx cat have a genetic abnormality which gives them their hairless appearance.

• Fungal infection: ringworm (dermatophytosis) is an example, which can cause destruction or damage to hair follicles.
• Parasites: fleas are the most common external parasite seen in cats. Associated hair loss usually occurs due to over grooming. Some cats are allergic to flea saliva which can make issues even worse. Mites (mange) and lice can also be found in cats.
• Bacterial infection: this is often secondary to another issue affecting the skin, such as allergies or parasites.
• Allergies: cats with underlying skin allergies will have itchy, inflamed skin and will be more likely to overgroom. This could include environmental (eg pollens or house dust mites) and food allergies.
• Protein deficiency or hormonal imbalances: can affect the health of a cat’s skin and coat.
• Underlying disease: some diseases can cause hair loss. Other conditions may cause discomfort and the cat may lick the painful area and cause a bald patch.
• Psychogenic alopecia: compulsive overgrooming behavior is often caused by stress. This can be due to changes in the household or a stressful event like a trip to the cattery. Cats may groom the hair on their flanks and back limbs until they are bald.

The most obvious sign of alopecia is thinning of an area of hair, or hair loss significant enough to create bald spots. Other changes on the skin may help your vet determine the cause of the alopecia. These include scabs, redness of the skin, excessive crusting or discharge, dandruff, or wounds. In some cases, such as with thyroid disease psychogenic alopecia, the skin may look relatively normal except for hair thinning or hair loss.

Cats with alopecia may or may not have itching. In some cases, the hair may pull out very easily when the pet is touched.

A medical history and physical examination findings can provide valuable information for your veterinarian. Your veterinarian will ask how long the hair loss has been going on and whether any other signs of illness have been observed. Physical examination findings may reveal evidence of underlying illness.  Your veterinarian may alternatively find fleas or “flea dirt” (flea feces) on a pet that has a flea infestation.

A diagnosis of alopecia means trying to identify an underlying cause. Depending on the findings of their physical exam and history taking, your veterinarian may recommend specific tests to obtain more information:

• Fungal culture: if ringworm is suspected, your veterinarian can pluck a few hairs from several areas on your cat’s skin and place the hair samples on a culture medium (a substance that is used to grow microscopic organisms). This can be tested to confirm a diagnosis of ringworm.
• Skin scraping: if your veterinarian suspects mites, samples of skin associated with the hair follicle can be tested. This involves using a scalpel blade to gently scrape several hairless areas of skin. Because these mites can live deep inside the hair follicle, the skin scraping must be deep enough to cause minor bleeding in order to capture samples that contain mites. These samples can be examined under a microscope to check for mites.
• Cytology: using a swab, or by gently touching the flat surface of microscope slide to the skin, samples of skin flakes and debris can be obtained for examination under a microscope to determine what types of inflammatory cells, skin cells, or bacteria may be present.
• Bacterial culture: if the skin is infected or wounds are present, your veterinarian may collect some of this material to identify specific bacteria.
• Skin biopsy: using local anesthesia (usually with sedation or general anesthesia) your veterinarian may want to obtain a small sample of skin tissue. This can be submitted to a diagnostic laboratory for examination of the skin cells, hair follicles, and other structures within the skin.
• Allergy investigation: if your veterinarian suspects that alopecia may be caused by skin allergies, a test to determine what your cat may be allergic to may be recommended, or a strict dietary food trial.
• Investigation into other diseases: if an underlying illness such as thyroid disease is suspected, blood testing or other specific diagnostic tests may be recommended.

Treatment for alopecia should involve treating the underlying cause. Fortunately, flea infestation, mange, pyoderma, and many other causes of alopecia are treatable conditions. Medications given by mouth (such as antibiotics, anti-inflammatories or antifungal medications), and topical products such as those used to control fleas may be recommended. Some cats with allergies may require ongoing management for their condition, using immunotherapy, allergy medications or dietary changes. Cats with psychogenic overgrooming may benefit from the help of a qualified pet behaviorist.

Once the underlying problem has been addressed, the hair follicles should recover over time. The hair will grow back if the hair follicles have not been permanently damaged or destroyed. However, if a skin infection or other skin trauma has been severe enough to damage or destroy hair follicles, areas of baldness may remain.