A bite from one flea can cause allergic dermatitis. This is a severe reaction to the saliva of the flea and causes itching, redness, hair loss, infection and hot spots. Advantage is one flea medication recommended by veterinarians. Hot spots are itchy, inflamed, raw areas that can occur in breeds of dogs that have thick hair and long, oily coats. These include akitas, chows, cocker spaniels and golden retrievers. Hot spots could be triggered by an insect bite. Lice can cause itching, rough hair and hair loss. This should be treated with permethin. Food allergies can cause dogs to itch all over. Dogs with food allergies need to be on a prescription trial diet for two or three months that includes smaller protein molecules which don't trigger the immune system. Another type of allergy, anine atopy, results in itching and loss of hair because of pollen and other allergens. Solar dermatitis is a reaction to sunlight that causes redness, hair loss and scales on the ears and nose. This is common in collies and shelties.
Infections and Fungus
Ringworm is a fungus passed on by contact or by being groomed with combs or clippers that have been used on an infected animal. The fungus weakens hair shafts, causing the hair to break off. Ringworm can be treated with fluconozole or topical iodine applications. Mange is caused by a parasite that lives in the hair and oil glands the the dog's skin. It can be treated with ivermectin. Folliculitis is an infection of hair follicles by bacteria, such as staph. Antibiotics should be given to the dog for at least four weeks.
Conditions and Diseases
Hypothyroidism, a decrease in the thyroid hormone, is the most common hormonal disease that causes hair loss in dogs. Hair becomes dry and brittle, seborrhea can develop, and dogs can become obese. Thyroid medication is needed for the dog's lifetime. Diabetic dogs can develop skin infections that cause hair loss. Changes in diet and insulin are necessary for treatment. Nervous or stress and boredom induced dermatitis is common when a dog is left at home while the owners work. It also occurs in older or obese pets and is hard to cure. To prevent dogs from licking and biting until their hair is gone, behavior modifying medication is necessary if the underlying cause can't be resolved. Cushing's disease, caused by an increase of corticosteroids in the dog's body, can be treated with Mitotane or surgery to remove tumors.