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Hair Loss in Dogs

Ron Hines DVM PhD 2/20/03

Hair loss is one of the most common problems that bring dogs and cats to my animal hospital. There are an enormous number of reasons for hair loss; but I am going to go over a few of the more common ones.

When a pet with this problem enters my office, I make a few simple observations and ask a few simple questions. Is this a young or an old pet? What breed is it? How long has the problem been present and has it occurred before. If so, how was it diagnosed and treated the last time? Is it a single patch or on various areas? Is it on the body itself or on the face or limbs? Is the hair missing or broken or chewed off short? Is the area itchy to the pet? Is the hairless area raw and inflamed? Is it dry and crusty? Are the areas a particular shape? What other pets do the owners have? What do they feed this pet? What changes have occurred in this pet’s recent past? Are the owners themselves itching? Do the webs of the pet’s feet itch? Does it scoot? Are fleas or flea dirt present? What is the pet bathed in? Is this an emotional or nervous pet? What medications worked or did not work if the condition was treated in the past? What follows are some common causes of hair loss, presented in order of frequency that I see them in Florida.

1) Flea-associated dermatitis

This is a common problem in all the Southern States. Even a single flea can cause this problem and the flea or its waste can be very tough to find. This is particularly true in dark haired pets. One give-away is the distribution of the problem. For reasons unknown to me, fleas prefer the area just anterior to the base of the tail. A brittle, broken hair coat in this area with a characteristic musty (seborrheic) odor and or the presence of pepper-like granules that stain a wet paper towel are sure signs of flea involvement. In other cases, the bite of a single flea will set off itching of the entire body – but particularly the webs between the toes. Eventually, bacteria and yeast become involved. The best treatment is to apply a topical flea-control medicine such as Advantage or Frontline.

2) Canine and Feline Atopy

This is an allergic itching and subsequent loss of hair. In allergic people, the respiratory system is often involved. In dogs and cats however, it is the skin that is most involved. Unfortunately, antihistamines that are so effective in people are much less effective in our pets. There is no cure for pets that are allergic to things they breathe. If you move, they soon become allergic to material in their new environment. This is a genetic disease and it occurs in lines of dogs and cats. The animals are generally a year or so old when it is first noticed. Eventually, bacteria and yeast become involved. Treatment will make the problem more bearable to the pet. They can include antihistamines, soothing topical shampoos used weekly or biweekly, soothing anti-inflammatory topical ointments, bathing agents that keep bacteria and yeast in check, tranquilizers that lessen itching and when all else fails, judicious use of cortisone-like products. Some owners even resort to mechanical collars that prevent chewing but I do not.

3) Pyotraumatic Dermatitis (Hot Spots)

This is a problem in, long-coated thick-haired breeds of dogs with rich oily coats. Usually they are 2 years old or older Often, these are northern dogs, which have recently moved to Southern States. Golden Retrievers, Cocker Spaniels, Spitz, Samoyed, Chows, Akitas, and Pyrenees are some breeds that come to mind as over represented among dogs with this problem. It is a rarer problem in cats and when it does occur in cats, it is often subsequent to stress. Intense itching occurs in one or two isolated area of the trunk of the body. The area becomes inflamed, raw and wet with serum within a matter of hours. Some theorize an insect bite initiates the problem. If the dog is muzzled or restrained during this period, the problem passes in 24-72 hours. If not, when the area is painful enough, the pet ceases to bite at the area. It may reoccur every 4-8 months or never again. It is treated with a topical astringent/cortisone agent and often with an injection of anti-inflammatory drug as well. Antibiotics are generally not required.

4) Demodectic and Sarcoptic Mange

The first form, Demodectic mange, is generally a disease of young dogs. A parasite, which lives in hair and oil glands of the skin of all dogs, begins to multiply out of control. This is a genetic disease. It runs in certain lines of dogs and is more common in certain breeds of dogs (see article on mange). It causes no itching but the involved areas are subject to secondary bacterial infection. It is treated with Mitaban (amitraz) dips or with ivermectin. Ivermectin is dangerous to use in cats. Small lesions may disappear without treatment.

Sarcoptic mange is due to a transmissible parasite that burrows through the layers of the skin causing intense itching. It passes from pet to pet through contact. It will attack humans as well. It is easily cured with ivermectin given orally or by injection.

5) Ringworm
Ringworm is a fungus – not a worm. It is transmitted by contact or through some object – such as grooming clippers and combs. It is not itchy. It is often circular or oval in shape. The hair in the area is broken off – due to the fungus weakening the hair shafts. It is often located on a limb, ear or the face. It often glows in the dark under an ultraviolet light source (Woods lamp). It may spontaneously disappear (especially in cats) yet the animal remains a carrier of the fungus. It is treated with fluconozole, itraconazole, griziofulvin and topical iodine preparations.

6) Nervous or Stress/Boredom Induced dermatitis
This is quite common in the terrier breeds. It is more common in dogs than cats and more common when both of a couple works and the pet is left alone. It also occurs due to persistent licking of an area in older, obese or lame pets. Dogs are usually adults but can be any adult age at onset. It is hard to cure. Some treatments include topical bitters mists, relieving boredom, anti obsessive/compulsive behavior drugs such as chlomipramine, and taping isolated areas with a protective covering.

7) Food Allergies
Pets with this problem itch all over, all the time. Pets that are allergic to food or treat ingredients have cells in their skin that release histamine when the pet ingests certain proteins. All the preceding problems should be ruled out first. Then the pet should be placed on a 60 – 90 day trial diet restricted to a prescription brand in which the protein molecules have been made smaller (less than 10,000 Daltons). These smaller proteins are not recognized as “foreign” by the pet’s immune system. Lamb, and exotic ingredient diets are only helpful for a while. Then the pet becomes allergic to them as well.