Most people associate scratching in cats with fleas. While fleas are often the cause of this, there are many other possible causes of scratching in cats.

Cat Fleas:

Fleas are a common problem in cats. They are most abundant in the summer months, although in tropical areas may be found all year around. Signs of cat fleas include seeing small, black insects in the coat, grit like appearance in the cat's bedding & scratching.

If your cat has fleas, you will have to treat both the cat & your home. Your veterinarian will be able to advise on the best product to use on your cat. There are many excellent products on the market for cats, many of which are applied to the back of the neck. The environment will either need to be treated with a flea bomb  or a pest controller, along with some thorough washing & vacuuming. For further information on cat fleas read here, and for information on how to eradicate fleas on your cat & in your home read here.

Flea Allergy Dermatitis:

While the odd flea on most cats won't bother them too much, some cats will be hypersensitive to them. This is known as Flea Allergy Dermatitis (also known as flea bite hypersensitivity).

As the name suggests, it is caused by an allergic reaction to a flea bite. There are 15 known allergens in flea saliva, each one is capable of causing an allergic reaction in the cat. Just one bite from a flea is enough to trigger an allergic reaction in your cat.  FAD is one of the major causes of miliary dermatitis in cats.

Some symptoms include: frequent scratching & biting of the fur, especially on the back & the base of their tail. Other symptoms of flea allergy dermatitis include raised bumps (papules) or scabs on the skin & thinning fur in the affected area.

Your veterinarian will be able to diagnose flea allergy dermatitis. This can be done visually. Signs of fleas on your cat are a good indicator. However, extremely sensitive cats will have few if any fleas on them. This is due to excessive self grooming.   In such cases, to get a definite diagnosis that your cat is in fact allergic to flea bites & not something else then a intradermal skin testing is required.

Treatment involves:

Mites:

Mites are tiny members of the arachnid (spider) family. There are several types of mites in cats including  Notoedric Mange, Cheyletiellosis (walking dandruff), Lynxacariasis, Trombiculidiasis & Otodectic Mange (ear mites). Most of these are fairly rare in the cat so I won't go into detail.

Ear mites (Otodectes cynotis): Although the name would suggest otherwise, ear mites can live on any part of the body although they generally live in the ears of cats. They are the most common cause of otitis externa (inflammation of the outer ear canal) in cats.

Not all cats will display symptoms of ear mites but often they will scratch at their ears & or shake their heads. Other symptoms may include reddish/brown discharge in the ear,  bleeding from the ear, coffee-grounds like appearance in the ear, scratch marks, odour.

Treatment depends on how severe the problem is.  Removal of the exudates from the ear by instilling a few drops of mineral oil & gently massaging the base of the ear. This will loosen the exudate, which will make it easy to remove.

Notoedric Mange (feline scabies) is a highly contagious, intensely itchy skin disease, caused by the mite Notoedres cati. These mites are closely related to the Sarcoptic mange, which causes mange in dogs.

The first sign of notoedric mange is usually intense pruritus (itching) along with hair loss & a thick/crusty & scabby appearance to the skin, especially along the tip of the ears. It then progresses to the face & neck, & if untreated can progress to other parts of the body.

Scratching the affected areas causes the skin to become raw, red & inflamed, which can cause potentially dangerous secondary bacterial infections.

Diagnosis is made by taking a scraping of the cat's crusty skin examine it under a microscope for the presence of mites or mite eggs.

Treatment involves:

Cheyletiellosis (also known as walking dandruff) is a highly contagious skin disease cause by the Cheyletiellosis mite. Cats are most commonly infected with Cheyletiella blakei. Young cats are more often infected although cats of any age can have these mites.

Symptoms include pruritus (itching), excessive scaling/dandruff, crusting along the back.

Cheyletiellosis is diagnosed by flea combings, skin scrapings, fecal flotation or acetate tape preparations.

Treatment may include; lime sulfur or pyrethrin dips & or Ivermectin.

Allergies:

The word allergy means 'altered working'. Just like humans, cats can have allergies too. Allergies are a common cause of skin disease in cats.

The purpose of the immune system is to keep infectious microorganisms, such as certain bacteria, viruses, and fungi, out of the body, and to destroy any infectious microorganisms that do invade the body. Allergies are caused by an inappropriate response to a substance which would usually be considered harmless. In an allergic animal, the immune system over reacts to the substance & mounts an immune response against it.

In cats there are four types of allergies; insect (most often caused by fleas, but occasionally mosquito bites can cause an allergic reaction), food, contact & inhalant.

All the above causes have different symptoms, most of which are already covered in specific articles but scratching is often seen in the case of allergies.

Feline Miliary Dermatitis:

Miliary dermatitis (also known as miliary eczema, papulocrusting dermatitis or scabby cat disease) isn't a specific disease but a disease complex. It is characterized by a red & crusty rash around the head, neck & back, often with intense itching.

There are several causes of miliary dermatitis including flea bite hypersensitivity, Allergies; food intolerance, inhalant allergy, food allergy, bacterial infections, mites, mange, ringworm, yeast infections, immune mediated diseases, drug hypersensitivity, poor diet & hormonal/endocrine disorder.

Symptoms include: Red, crusty bumps, especially around the head, neck & back, often with intense itching, hair loss, scratching.

Treatment of feline miliary dermatitis depends on the cause of the problem.

Food Intolerance:

A food intolerance is an adverse reaction to a food, one of it's ingredients or additives. It differs from a food allergy in that the immune system is not involved. Food allergies typically cause non seasonal itching, especially around the head & face, swollen & inflamed areas on the face & ears, hair loss due to itching, vomiting & diarrhea.

A common food intolerance that many people have heard of is milk. This is because many mammals lack the enzyme necessary in order to digest the lactose in, which is the major sugar in milk.

The most common causes of food allergies & intolerances in cats are fish, beef, eggs, wheat &  milk.  Cats can become allergic & intolerant to foods they have eaten for a long period of time.

As you can see above, vomiting & diarrhea are symptoms which can also be displayed in a cat who is allergic to a food, however the allergic cat also has other symptoms such as itching, which is caused by the immune response.

Avoiding the food which caused the intolerances is the best method of treatment. This may either be a home made diet or a commercial one. If you are feeding a home made diet it is important to ensure that your cat is receiving the correct nutrients in the diet.

Ringworm:

Ringworm is the most common fungal skin infection seen in cats. Contrary to the name, ringworm is caused by a microscopic group of parasitic fungal organisms known as dermatophytes (which means "plants that live on the skin"). Ringworm invades the dead, outer layers of the skin, claws & hair.

The most recognised sign your cat is infected with ringworm is circular patches of hair loss, especially around the head & limbs (although it can occur on other parts of the body also). Other signs are grey, patchy areas of baldness, with or without redness & itching, seborrhea sicca (a type of dandruff), dry/flaky skin, onychomycosis (infection of the claw & clawbed).

Related articles:

Ringworm in cats, ringworm in humans, miliary dermatitis, cat fleas, ear mites, food intolerance, allergies