There are many diseases and conditions which can cause a dog to lose hair; some more common than others. This article will help reveal some of the least common causes of hair loss in dogs and cats and some of the most successful treatment options.

1. Chemotherapy - Loss of hair due to chemotherapy.

Symptoms: Dogs with continuously growing hair (e.g. Poodles and Maltese), often lose some hair; some may also lose whiskers.

Treatment: Hair will regrow after chemotherapy is discontinued; be aware hair may regrow in a different color or texture.

2. Cyclic (cicatrical) Alopecia - Growth cycle of hair stops at certain times of      the year.

Symptoms: Symmetrical hair loss with definite borders; usually on back and flanks; skin may become darker.

Treatment: None.

3. Diabetes Mellitus - Abnormal immunity makes diabetic dogs susceptible     to infection and other skin conditions.

Symptoms: Thin skin; some hair loss; seborrhea; recurrent bacterial infections; unregulated dogs also have many other signs of disease; may develop epidermal metabolic necrosis or xanthoma.

Treatment: Dietary changes; insulin.

4. Erythema Multiforme - Hypersensitivity reaction to infections or drugs;     may also be caused by cancer or other diseases.

Symptoms: Hair loss, 'bull's-eye' lesions, and vesicles often around mouth, ears, groin, and axilla; in some instances, ulcers develop; depression, fever.

Treatment: Treat or remove underlying cause.

5. Estrogen Responsive Dermatosis (ovarian imbalance type II) - More     common in young spayed dogs, and in Dachshunds and Boxers.

Symptoms: Hair loss starting at the genital area and flanks and moving forward; hair color may fade; coat is similar to a 'puppy coat'.

Treatment: Estrogen replacement therapy; caution - can have severe side effects.

6. Flea Allergy Dermatitis - Severe reaction by the animal to the saliva of     the flea.

Symptoms: Intense itching, redness, hair loss papules, crusts, and scales; sometimes development of infection or hot spots.

Treatment: Flea control in the environment and on the dog; steroids and antihistamines to help control the itching.

7. Growth Hormone Responsive Alopecia - Not well understood; thought     to be caused by an enzyme deficiency or decrease of adrenal hormones,     which allows certain other hormones to accumulate in the body. (more     common in Pomeranians, Chow Chows, Keeshonden, Samoyeds, and     Poodles).

Symptoms: Hair loss on neck, tail, and the back of the thighs; skin darkens; usually starts when dog is less than two years old.

Treatment: Neuter animal; growth hormone; hormonal supplementation.

8. Hyperestrogenism (ovarian imbalance type I) - Rare disease in which     female animals have excess levels of estrogen; can be caused by cancer     of the ovaries.

Symptoms: Symmetrical loss of hair; hair pulls out easily; darkening of the skin; enlarged nipples and vulva; may rarely see seborrhea and itching.

Treatment: Spay; look for metastasis to the lungs.

9. Leishmaniasis - Caused by a parasite of blood cells; can be transmitted     to people who develop a very severe disease.

Symptoms: Hair loss, scaling, ulcers on nose and ears, sometimes nodules; many other nonskin-related signs.

Treatment: Because it causes severe disease in people, and treatment of dogs is not curative, euthanasia may be necessary.

10. Lice - Infection with several species of lice.

Symptoms: Variable; itching, hair loss, crusts, rough hair coat.

Treatment: Pyrethrin, ivermectin, Permethrin (Do NOT use permethrin on cats).

11. Pattern Alopecia - Three types; hair loss may occur on the ears of       Dachshunds (pinnal alopecia); neck, thighs, and tail of American Water       Spaniels and Portuguese Water Dogs; abdomen and the back of the       thighs of Dachshunds, Chihuahuas, Whippets, and Greyhounds.

Symptoms: Hair loss in areas described above.

Treatment: None.

12. Pelodera Dermatitis - Accidental infection with larvae from a
       non-parasitic worm that lives in straw and other organic material.

Symptoms: Affects areas of skin touching ground; intense itching, redness, hair loss, papules, crusts, and scales.

Treatment: Remove bedding; mild antibacterial shampoo; steroids if necessary to control itching.

13. Pituitary dwarfism - Hereditary condition in which the pituitary gland       does not produce the necessary hormones.

Symptoms: Young puppies fail to grow; dogs retain puppy coat and condition progresses to hair loss over much of the body; thin skin, scales, and secondary infections.

Treatment: Hormone replacement therapy.

13. Sertoli Cell Tumor - Tumor of the testicles in middle-aged dogs.

Symptoms: Male dogs take on female sexual characteristics; hair loss, increased skin pigment, and reddened area on prepuce.

Treatment: Castration.

13. Testosterone Responsive Dermatosis - More common in old
       neutered dogs, and in Afghans.

Symptoms: Dull, scaly, dry coat; seborrhea; hair loss in genital and anal areas progressing onto trunk.

Treatment: Testosterone replacement therapy.

13. Vitamin A Responsive Dermatosis - May not be due to an actual       deficiency of Vitamin A, but does respond to increased levels of
      Vitamin A in the diet (more common in Cocker Spaniels).

Symptoms: Seborrhea; odor; hair pulls out easily; pads of feet thickened; thick scales on chest and abdomen, especially around nipples.

Treatment: Lifetime treatment with Vitamin A.

These articles on hair loss were provided to help you better understand some of the causes, both common and rare, that may affect your pet. As with any condition that affects your pet, it is always best to consult with your veterinarian if you have any concerns or questions.

These articles are not provided as a substitute for diagnosing any of these conditions.