Hair loss in cats is almost always due to excessive grooming from itchiness (pruritus). They often do this in secret so may not be seen. In the UK, fleas are the most common cause of this over-grooming. The general veterinary approach to skin disease: fleas are the culprits until proven otherwise.
It is thought that since cats groom to make themselves feel better, stress may also be a trigger, which may even lead to compulsive over-grooming. There is no strong evidence to support this as yet but, anecdotally, taking steps to relieve anxiety in the household may help, such as by using products like Feliway (a synthetic pheromone thought to give cats happy vibes).
Pain may also cause over-grooming. For example, with bladder disease, some cats will lick around their inner thighs, belly and genitals.
In people and in dogs, hair loss is often hormonal, but in cats hormonal skin disease is extremely rare. Genuine hair loss like this usually leaves behind skin that is smooth and soft to touch compared to spiky skin with over-grooming.
How can I tell if my cat has fleas?
Cat fleas are a few millimetres long and fast-moving. They can be hard to spot unless there are large numbers, especially in black cats! Given that each flea can lay 50 eggs per day, even a few fleas can cause a big problem. Not seeing fleas does not rule them out, especially as cats will eat many of them while grooming. Use a fine-toothed comb to groom your cat, tapping any debris onto damp cotton wool. Black specks that turn reddish brown with water, due to the blood contained in the flea poo, is evidence enough. Cats may show no signs but others will scratch, have hair loss, or scabs. Some cats are allergic to flea saliva, and the scabbing, hair loss and itching can be severe. Fleas can also spread tapeworm if eaten by your cat.
Can anything else cause my cat to itch or have hair loss?
Although fleas are the most common cause of itching, other causes include:
Ear mites are most common, but others are possible. Ear mites usually only affect the ears, but can cause hair loss behind the ears due to itching and can infect the head, neck and even the tail/rump as the cat sleeps curled up. Your vet can easily diagnose ear mites by examination under magnification and can prescribe simple treatment. Other mites live inside the skin, and some can spread between species, but again, there are simple treatments to eliminate infections.
- Food allergies (or intolerance). We are unsure exactly why certain foods can make a cat itch, but it is known that changing to a diet the cat has never had before can, in some cases, cure their itch. If this is suspected, a 6-8 week diet trial can be done. This can’t just be changing brands as it needs to contain products the cat has never eaten before. Your vet can recommend a hypoallergenic diet, and remember no treats (including mice!).
- Atopic Dermatitis. We know less about this condition in cats than dogs. In dogs, it is deemed as an inherited predisposition to developing allergic reactions to things in the environment, such as pollen or house dust mites. While it is thought that it occurs in cats, we don’t yet know if it is inherited. Diagnosis is by ruling other causes out. Skin and blood tests used in dogs to find the specific allergen are not yet that reliable in cats. Treatment usually involves corticosteroid or other immunosuppressive therapy, usually long term. Essential fatty acid supplements and antihistamines may help in some cases.
Other possible causes:
- insect bites. Bites from wasps, bees or other insects can irritate any cat but some cats can have a severe reaction to flea or other insect bites causing extreme itching. Mosquito bites are linked to an extreme hypersensitivity reaction known as eosinophilic granuloma.
- bacterial and yeast (Malassezia) These are uncommon and often secondary to allergic skin disease and can cause itching, thus hair loss.
- fungal disease. This can cause itching, but most often causes circular patches of hair loss. Often known as ‘ringworm’, it has nothing to do with worms! Ringworm is infectious to people, especially if immunosuppressed. Roughly half of cases fluoresce under UV light, which vets can test using a Wood’s Lamp. If this test is negative and ringworm is still suspected, treatment may be started on appearance alone or on results of fungal cultures. Treatment usually involves a long course of oral medication, and home decontamination.
- hormonal disorders. Cushing’s disease and hypothyroidism are extremely rare in cats. Hyperthyroidism is a common condition and some cats can develop hair loss with this, although other symptoms such as weight loss, increased appetite are normally more noticable.
- drug reactions. Although these are also rare, reactions can occur locally, for example, where a flea spot-on or collar has been applied, or due to certain oral medications.
What can I do?
If your cat’s hair loss is mild with no other symptoms you could try flea treatment first.
95% of the lifecycle of the flea is in the house so it’s important to treat the environment as well as all pets. Powders, over the counter collars and most aerosol sprays are best avoided. There are many tablet and spot-on options depending on your prefered route of administration and frequency. Consult your vet as there are many products available in shops and online that are not only ineffective but also potentially dangerous. Treatment needs to be regular and for all pets, as when it wears off your pets and home are susceptible again. Preventing fleas is always better than treating, especially if you have a pet that is allergic to flea bites. Safe and effective sprays for the house can also be bought from most vets. NEVER use a dog flea treatment on a cat, as it may be toxic to your cat.
If the hair loss is not mild, if there are other signs, or you have been using a veterinary flea preventative regularly on all pets, you should book an appointment to see your vet.