Causes of Scabs on a Cat’s Back

The presence of singular or multiple scabs on a cat’s back is a common symptom and one I battled with this in one of my cats for quite some time. We look at this, as well as other causes of scabs on the back.

Causes

Flea bite allergy: The most common cause of scabs on the back is miliary dermatitis caused by an allergic reaction to the saliva of a flea bite. This makes up approximately 80% of cats with miliary dermatitis. Just one flea bite is enough to trigger an allergic response.

Other allergies: Food, inhaled, and contact allergies.

Skin infection: Most skin infections are due to an underlying condition which may include hypothyroidism, Cushing’s disease,

Mites: Cheyletiellosis, notoedric mange, and demodicosis.

Ringworm: A parasitic fungal infection which occurs most often in cats in over-crowded conditions, young kittens and immunocompromised cats.

Abscess: A walled-off collection of pus most commonly due to a cat bite. Eventually, the abscess will rupture and scab over.

Symptoms

Miliary dermatitis:

Small, dry, hard, millet-like scabs on the back, close to the tail and around the neck. The skin on the back feels dry and gritty, and the cat’s skin may twitch.

As the neck is easier for the cat to scratch, trauma to the area can occur, resulting in open wounds where the cat has damaged the skin.

Other symptoms associated with miliary dermatitis include itching and hair loss.

Ringworm:

Circular, scaly red lesions which start small and increase in size, pustules, and itchiness. Lesions are most common on the head and ears although can develop on any part of the body.

Mites:

Areas of thinning hair or hair loss, crusting skin, intense itching. Secondary skin infections are common.

Abscess:

A singular, firm, marble-sized painful lump. Other symptoms include fever, lethargy, and loss of appetite.

As the abscess grows in size, the skin thins out and eventually, the abscess will rupture. There will be a foul-smelling discharge from the affected area.

Skin infection:

Crusts and scales, often with short hairs which are easy to pull out. Alopecia (baldness), itching may or may not be present and an unpleasant odour to the skin.

Diagnosis

The veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. Questions they may ask include:

• How long have the symptoms been present?
• Is the cat up to date on flea treatment?
• What product are you using for fleas?
• Does the cat go outside?
• Do symptoms come and go?
• Are there any other symptoms you have noticed?
• What is the cat eating?
• Is the cat on any medications?

Miliary dermatitis is easy to diagnose based on presenting symptoms. Other tests the veterinarian may recommend include:

• Analysis of coat brushings and fur samples: To check for parasitic infections such as mites, fleas or fungal infections.
• Skin prick test: An area of skin is shaved, and a tiny amount of several common allergens are pricked onto the skin to see if there is a localised reaction, which can pinpoint an allergy to a particular substance.
• DTM (dermatophyte) culture: Hair is plucked from the affected area, or a toothbrush will be used to collect samples which are then cultured on a special medium to check for fungal or yeast infections.
• IgE test: To look for the presence of IgE antibodies in the clear portion of blood.
• Skin scrapings: Scrapings of several layers of skin which are then evaluated under a microscope to look for the presence of mites, fungal infections, and bacterial infection.
• Skin culture: A sample of skin is taken from the affected area and added to a culture which promotes the growth of microorganisms which can identify a bacterial infection.
• Food trials: If a food allergy is suspected, the cat will be switched to a hypoallergenic diet for several weeks to see if symptoms improve. If they do, the cat is challenged with his old diet to see if symptoms return.

Treatment

Miliary dermatitis:

• As the most common cause of miliary dermatitis if cat fleas, the veterinarian may prescribe a flea treatment to see if symptoms improve. Not all cats respond to all flea treatments.
• Only the adult flea lives on the cat, the majority of the cat’s flea life-cycle is in the environment; therefore, it is important to treat the home as well as the cat.
• Corticosteroids to relieve itching.
• Antibiotics to treat secondary bacterial infections.

Other allergies:

• Identification and elimination of the substance causing contact allergy.
• Corticosteroids or antihistamines to relieve itching.
• Antibiotics if a secondary bacterial infection has developed.

Mites:

Treatment may vary depending on the type of mite, but can include the following:

• Weekly dipping with either lime sulfur or pyrethrin for 6 – 8 weeks. It may be necessary to clip cats with long hair.
• Daily or weekly oral ivermectin for four weeks. It is important to monitor the cat during treatment.
• Wash bedding and blankets in hot water, hang in the sun to dry.
• Treat all cats in the household.

Ringworm:

• Oral anti-fungal drugs, medicated baths and/or medicated shampoos and dips. It is important to clean the environment at the same time as the cat is treated with a 1:10 bleach solution.

Skin infection:

• Find and address the underlying cause where possible as well as antibiotics to treat the infection.

Abscess:

• Surgery to open the abscess if it has not ruptured, followed by flushing the wound with antiseptic and antibiotics.