You know you have a healthy cat when they have a shiny, soft, thick coat. However, when you start to notice that your cat seems to be losing a substantial amount of fur, this can be worrisome, especially if their hair loss is coupled with excessive scratching. While it is normal for your cat to shed some of his fur (like in the summer when he begins to shed his winter coat), if he is losing a lot of hair or losing his hair in clumps, it may be cause for alarm. If you also notice other feline skin issues like sores and inflammation, then something is definitely off, and you know there must be a more serious reason for your cat’s hair loss. So, what causes hair loss in cats? There are several potential causes, but here is a short list of the most common.

Allergies

Skin allergies, or allergic dermatitis, in cats, are the biggest cause when it comes to hair loss. On top of hair loss in cats, you may also notice hotspots and patchy skin that looks irritated or inflamed. Unfortunately, it can be hard to narrow down the source of the allergen. Allergens can be environmental or food-based, and sometimes it takes a process of elimination to figure out which your cat suffers from. The most common feline food allergies are to the protein or carbohydrate content of their food.¹ If a food allergy is suspected, an elimination diet should be started to find the culprit. Once you do pinpoint the allergen and remove it, your cat's woes should clear right up, and his hair should grow back in as normal.

Psychogenic Alopecia

This is a fancy name for compulsive grooming. Compulsive grooming is a mental disorder where your cat will groom himself excessively - biting, chewing, and licking so much that he pulls out his hair and even create sores, irritation, and infection.²

Notoedric Mange

This is the result of a parasite, and you may notice hair loss on your cat’s face and upper body, especially around the neck, eyelids, and ears.³ This parasite is the second most common pest to plague cats.

Eosinophilic Granuloma

Vets do not currently know the exact cause of this condition, but your cat will develop lesions and lose the hair on the backs of his legs.⁴ It is thought that this condition is related to allergies somehow, but no one knows for sure.

Demodectic Mange

Demodectic Mange is a common cause of itching and hair loss in cats, caused by mites burrowing under the skin.⁵ These bugs can cause quite a bit of itching but are so tiny; they are invisible to the naked eye.

Ringworm

Ringworm is a fungus and will manifest on your cat as hair loss in little circular patterns. Because this fungus infects the shaft of the hair, sometimes it's necessary to shave your cat after treatment to make sure the fungus is completely removed.

Fleas

A very common condition found in cats is something called flea-based alopecia, where the cat is very sensitive to flea saliva. The result is hair loss in a patchy pattern, coupled with… you guessed it… itching.⁶

Cushing's Disease

This disease is rare in felines, but when your cat has it, he will lose hair on both sides of his body.⁷ Your cat also may present with other symptoms such as lethargy and increased thirst and appetite. You may also find that your kitty doesn't enjoy a good petting the way he used to because his skin is too sensitive.

Thyroid Disease

Just like people, cats experience thyroid issues too, such as hypothyroidism. Unfortunately, hypothyroidism can also be a culprit for hair loss in cats. With hypothyroidism, hair can become very brittle and dull and fall out when you pet or brush your cat.

Feline Endocrine Alopecia

This is a condition where your cat loses hair on his inner legs, abdomen, and genital area. It is thought to be related to hormone levels. However, whatever it is related to, the condition is rare. As you can see, though we can’t always know what causes hair loss in cats, there are a variety of possible conditions to look at. Some of them can be more severe than others, so if you do notice that your cat appears to be grooming himself more than usual, or that his hair seems to be disappearing in clumps or patches or odd places, it’s much better to be safe than sorry. Take your cat in to see a vet and let them help you figure out the source of the problem and get your cat's skin and coat looking better in no time!

References:

1 http://www.vet.cornell.edu/fhc/Health_Information/foodallergies.cfm

2 https://vcahospitals.com/know-your-pet/cat-behavior-problems-compulsive-disorders-in-cats

3 http://www.aavp.org/wiki/arthropods/arachnids/astigmata/notoedres-cati/

4 https://vcahospitals.com/know-your-pet/feline-eosinophilic-granuloma-complex-in-cats

5 https://www.banfield.com/pet-healthcare/additional-resources/article-library/conditions-illnesses/demodectic-mange-overview

6 http://www.vetmed.ucdavis.edu/vmth/small_animal/dermatology/factsheets.cfm

7 http://www.petmd.com/cat/conditions/endocrine/c_ct_Hyperadrenocorticism?page=show