Dog Hair Loss: Causes, When to Worry and What to Do

What it usually means

Alopecia means partial or complete loss of hair in places where it normally grows. It is a sign of something else going on, so the cause has to be found before it can be treated well.

The pattern gives clues. Loss can be in one spot, in several patches, or symmetrical on both sides of the body. Itchy dogs scratch and chew hair away. Hereditary hair loss is often symmetrical, and hereditary and hormonal hair loss usually look calm rather than inflamed unless a skin infection sets in. Hairs may fall out from the follicle or break off partway, and a vet can often tell which by looking closely.

Normal shedding is different. Shedding without bald patches or symmetrical thinning is usually fine, and seasonal undercoat shedding is rarely a concern. The signs that something is wrong are bare skin, thinning that you can see, redness, scaling, thickened or darker skin, scabs, or a dog who cannot leave the area alone. Common triggers include fleas, allergies and itching from other causes.

Common causes

What you can do at home

Home care here is about gathering clues and avoiding guesses. Take photos of the affected areas and repeat them every few days so your vet can see whether the loss is growing. Write down when it started, whether your dog is scratching or licking, any fleas you have spotted, and anything new in the home, such as a diet, shampoo or bedding.

Check that the collar or harness is not rubbing. Keep up with the flea and tick prevention your vet recommends, and ask whether the house and bedding also need treating if parasites are involved.

Resist treating it yourself. Mites, fungus, bacteria, allergies and hormones all cause hair loss, but they need very different treatments, and a wrong guess can delay the right one. That includes leftover medicines, human creams and home remedies. Mange in particular is something to have confirmed, because sarcoptic mange can spread to other animals and to people, so limit close contact with other dogs until your vet has had a look.

Feed a complete and balanced diet, and groom regularly to manage normal shedding.

What happens at the vet

Your vet will ask about your dog's breed, when the loss began, how it has changed, whether there is itching, and what products and parasite preventives your dog gets. The exam looks at the pattern of loss and for signs of infection, parasites and inflamed skin.

Expect some simple tests. Combing the coat can turn up fleas, and skin scrapings are examined under a microscope for mites. Skin smears and cultures check for bacterial, yeast and fungal infection. If a hormone problem is suspected, blood and urine tests come next, and a skin biopsy can help when the cause stays unclear.

Treatment follows the cause. Parasites are treated and the environment cleaned. Infections get antibiotics or antifungals. Itching and inflammation are treated with medication. Hormone problems are treated with medication that corrects the imbalance. Hair loss that is purely hereditary often needs no treatment at all if it does not bother your dog.

Finding the cause can take time, so vets often treat the itch or discomfort in the meantime. Demodectic mange is rechecked with monthly skin scrapings until two in a row come back clear, which can take several months.

Prevention

Not every cause can be prevented, but a few habits cut the odds. Because fleas and mites are common triggers, the parasite prevention your vet recommends is the most practical step. Check your dog over during grooming sessions so you notice early thinning, scabs or rubbed spots before they grow.

Keep a well-fitted collar or harness, and have skin injuries and itching looked at early rather than letting a dog chew at them.

Feed a complete and balanced diet suited to your dog's age and activity level. Regular checkups also give your vet a chance to catch hormone disease, which can show up as a thin or changing coat.

Dogs that have had demodectic mange should not be bred, since the tendency may be inherited.