Q & A: Hairloss

By Dr. Kim Everson, DVM

 

Question: My dog is losing hair all over her body. What causes that?

 

Answer: Hair loss in pets happens for any number of reasons. A thorough examination by your veterinarian combined with a detailed history and some skin testing will be necessary to figure out why your dog is losing hair and how to treat or manage her condition. Here is an overview of what your veterinarian will be checking for.

One of the first things your veterinarian will do is ask a bunch of questions about your dog’s hair loss such as how long it has been going on, if she seems itchy or not, if she spends time around other animals, if you treat her regularly with flea and tick medicine and if she has any other physical complaints. This helps sort out whether the problem stems from allergies (including food, seasonal or indoor), parasites or some other issue.

Next, your veterinarian will examine your pet looking for obvious signs of parasitism such as fleas or “flea dirt.” Fleas can be very difficult to find, but animals with fleas will often have black specks of “flea dirt” on their skin, which is the flea’s digested blood meal.

Other parasite tests may also be done including a scotch tape prep and skin scrape. A piece of clear cellophane tape is stuck to places of interest on the pet’s fur and skin to trap invisible bugs. The tape is applied to a glass slide and examined under the microscope. Several types of mites, lice and some other microorganisms may be seen using this test.

Another test for mites is a skin scrape.  Just as it sounds, this test involves scraping the skin enough to cause a small abrasion. The scraped off material is placed on a glass slide and examined under the microscope. Treatment for mites, lice, fleas and other external parasites varies dramatically depending on the insect found, so knowing exactly what is plaguing the pet is essential.

Another infectious cause of hair loss is a fungal infection called ringworm. Ringworm fungus can affect many types of animals including dogs, cats, cattle, horses and people! In fact, ringworm can be spread between animals and people. While in people ringworm appears on the skin as a “ring-like” rash, in animals it tends to cause patchy hair loss and brittle, dry hairs. A neat test called a black-light test can be done to screen for ringworm. Using a special light called a Wood’s lamp, your veterinarian will examine an area of interest for green, glowing (fluorescent) hairs. Only about 50% of ringworm cases “glow” and other features on the skin and fur (like lint or scabs) glow as well, so your veterinarian may also need to examine hairs microscopically and start a fungal culture as well to be sure of a ringworm case.

Any scabs, sores or rashes may then be sampled with a swab or glass slide. The slide will be examined under the microscope to determine if your pet has an overgrowth of bacteria and/or yeast. An impression smear that is positive for bacteria or yeast may not provide all the answers as to why your pet is losing hair, but certain medications will be needed to treat these infections. Bacterial and yeast infections often happen because of another problem like parasites or allergies.

Most people think of allergies nowadays when their pet loses hair or becomes itchy. It is true that allergies are a common complaint in pets, but a diagnosis of allergy requires a thorough understanding of the pet’s history, skin testing as described above, response to various anti-itch medicines and careful elimination or hypoallergenic diet trials. Allergy testing can be done via a blood test or intradermal skin testing (a skin-prick test) in pets afflicted by hay fever and indoor allergies. This is usually done to create hypo-sensitization treatment, or allergy injections to lessen the severity of the allergy response over time.

Not all hair loss is the result of infection, parasites or allergies. Thyroid disease and other metabolic disorders can cause skin and hair changes ranging from subtle to dramatic. A variety of laboratory tests including blood work can help identify if a systemic illness is causing the changes.

Finally, really challenging cases of hair loss may require a skin biopsy for diagnosis. Baldness or poor hair growth due to rare chemical imbalances or genetic predisposition can happen in pets just as in people. Once the cause of baldness has been determined, medications or natural supplements may be used to manage the problem.

As you can see, hair loss in pets may stem from a wide variety of internal and external causes. The best chance of successfully understanding and treating hair loss relies on your observations as a pet owner, your veterinarian’s systematic examination of the problem and good compliance with treatment recommendations including follow-up visits to monitor your pet’s progress.

 

Originally printed in Pet Journal, April 2014