A cat losing hair on its hind legs is cause for concern. It's normal for a cat to be shedding, but sudden loss or thinning of hair on the back legs is not. Hair loss in cats, also known as alopecia, can be caused by a variety of issues from fleas, allergies, a bacterial infection, or stress, all of which are problems that must be addressed. Know the difference between normal shedding and abnormal hair loss so you can react appropriately.

Why Do Cats Lose Hair on Their Hind Legs?

Hair loss occurs in response to many factors, including poor nutrition, autoimmune disease, fungal infections, allergies, and parasites. Cat hair loss can be partial or complete, and the patterns can vary or be symmetrical. The skin surrounding the area of hair loss can appear normal, or it can have redness, bumps, and scabs. Hair loss is a symptom, and the underlying cause must be determined in order to be treated. If a cat has hair loss and is scratching the area excessively, the itching problem should be investigated first. Below are four of the most common causes of hair loss on hind legs in cats. 

Fleas and Other Parasites

Fleas are one of the most common reasons to see hind leg hair loss in cats. Fleas are no fun for any cat and can cause your cat a lot of discomfort, many cats develop an allergy to flea bites. Flea bite hypersensitivity (allergy) or flea allergic dermatitis (FAD) is very common in cats.  In these cats, just one flea bite can cause severe and prolonged itching which often results in hair loss and can lead to open sores or scabs on the skin, allowing a secondary bacterial infection to occur. Many cats will excessively chew or lick the hair off their legs when they have fleas or FAD.  Hair loss around the neck, legs, and base of the tail can also be seen along with small crusty scabs called miliary lesions, a term that was coined because the scabs look like millet seeds.

Since the flea saliva causes the reaction, the most important treatment for flea allergy is to prevent fleabites. Both indoor and outdoor cats can get fleas and it is recommended to keep your cat on a veterinary approved flea prevention monthly to prevent fleas.  

Other parasites, including mites and ringworm can also cause excessive scratching, licking, or chewing, but fleas are the most common to cause hair loss on hind legs. 

Pain

Cats who are exhibiting pain can over-groom the areas that are painful. Feline lower urinary tract disease and arthritis are two common causes of pain and discomfort for cats. In response to this pain, they may over-groom to the point of hair loss on their lower belly, the inside of their hind legs, and around their genitals. 

Pain can be difficult to assess in cats and it is important to be aware of signs of pain in cats and to contact your veterinarian. 

Always consult your veterinarian for an appropriate pain therapy plan. Their plan can include pain medications, laser therapy, acupuncture, and supplements.

Allergies

Food, environmental, and flea allergies as mentioned above may also be part of the reason why your cat is experiencing hair loss on their hindlegs. The first step in treatment of allergies is to find the source of the allergen and eliminate it. When it comes to food allergies, most cats are actually allergic to a protein and not other nutrient sources. A hydrolyzed diet is a food that has gone through a process where the protein is broken down into its individual amino acid components. This prevents your cat's immune system from identifying the food as containing an allergen and prevents your cat from having symptoms of an allergy flare up. Other allergens, such as mold in the environment can cause itching, scratching, and overgrooming.

Stress and Anxiety

Cats are meticulously clean creatures and fastidious groomers. Cats typically spend between 30 percent and 50 percent of their day grooming themselves. However, if your cat is grooming themselves to the point of hair loss or skin wounds, they can be suffering from an underlying medical as noted above or psychological issue.

Grooming is a normal reaction of cats to make themselves feel better during stressful situations or when they are anxious. This can become compulsive if the grooming behavior is performed out of context and so frequently that it disrupts normal activity. The areas cats commonly over groom due to stress include the abdomen, inside of the thighs, and the lower back. Cats may groom excessively when the caregivers are not present, so it can be difficult to note. Most caregivers will notice areas where the hair is thin or absent. Some cats will lick in one area alone while other cats may groom excessively in more than one area.

Compulsive grooming, also known as psychogenic alopecia, is usually triggered by a change in the cat’s daily routine or environment, such as moving to a new house or the arrival of a new family member or pet. Other stressors can include tension between cats, too much competition for resources, and boredom.

It is important to have medical issues ruled out by your veterinarian. Cats with psychogenic alopecia will often have hair loss without inflammation of the skin, although severe overgrooming can result in secondary infections and irritation, and your cats hair under a microscope will appear pulled out entirely or broken off near the skins surface.

The treatment is to establish an underlying cause with your veterinarian, identify any stressors and eliminate them if possible, provide mental and physical enrichment, maintain consistent routines, and create a less stressful environment. You can create a less stressful environment by adding hiding and vertical places for your cat, playing with your cat more, and using products that mimic a chemical that cats emit through the glands on their faces when they are feeling calm and want to communicate that to other cats in the area.

How to Prevent Hair Loss

Not all of the causes of hair loss in cats are preventable. However, you can take steps to keep your cat as healthy and happy as possible.

• Ensure that your cat's personal stressors—whether it's a change in its environment or another animal—are kept to a minimum so it does not resort to over grooming out of frustration.
• Provide a nutritious diet, plenty of exercise, and regular veterinary checkups to bypass serious health issues.
• Keep your cat on effective flea prevention monthly to prevent infestations of parasites that can cause hair loss.
• Keeping your cat inside can reduce its exposure to many mites as well.

Cats can lose fur on their hind legs due to a variety of issues. The first step in treatment is finding out the underlying cause of the hair loss. If you notice your cat is losing hair, take your cat to your veterinarian for an exam. The sooner the cause is diagnosed, the sooner the cat can be feeling better and growing back their coats.