About Patches of Hair Loss in Dogs

The Facts

• A dog's coat constantly replenishes itself. The hair grows in a cycle: Some hairs fall out as follicles go dormant, hairs grow as follicles activate, and other hairs are waiting just beneath the surface of the skin for the follicle to become active so they can grow. If your dog experiences patches of hair loss leading to bald spots, that is a signal that your dog may have a parasite, a skin infection or another health condition.

Fungal Infection

• One cause of patches of hair loss in dogs is a fungal infection. Ringworm is an extremely contagious condition. When a dog has ringworm, fur falls out in small circular patches. The bald skin that is revealed can be marked by red lesions that form a circle. Dermatophytosis is another fungal infection that causes patchy fur loss. These infections can be easily treated by a veterinarian. Once the fungal infection has cleared up, your dog's hair will grow back normally.

Mites

• Mites can cause a dog to lose hair. These tiny insects live in your dog's hair follicles. If your dog has hair loss in patches that are especially pronounced around the head, neck or feet, then he might be infected with mange. Depending on what kind of mite is causing the mange, it could be passed on to humans. Demodicosis is caused by Demodex mites and also causes patches of hair loss. A veterinarian can determine which mite is causing the problem and prescribe a rinse or injections to eliminate them.

Allergies

• If your dog is losing fur in patches and is scratching more than usual, then allergies might be to blame. If you washed your dog's blanket with a new detergent and your dog is allergic to a chemical in the detergent, that can lead to skin irritation and itching. If it is bad enough, your dog can scratch its fur out and create bald patches. Removing the allergen will stop the allergic reaction and the hair loss should stop.

Other

• Other causes of hair loss in patches in dogs include bacterial infections, which can be cured with antibiotics and should not cause lasting baldness. Some dogs experience acral lick dermatitis, which can be triggered by boredom. The dog will compulsively lick or scratch at a patch of skin until all the hair is worn away, leaving a bald patch behind. Because this is often a psychological issue, it can be difficult to treat successfully.