Common parasites include flies, ticks and Sarcoptic or Demodectic mange.
Fleas are extremely common in dogs and cats. Sometimes they can be difficult to eliminate, especially in situations with multiple pets or frequent exposure to other pets. Flea collars are generally not very effective for treatment for the problem and may actually cause skin reactions in some dogs. Successful treatment may involve an intense, well-thought-out treatment plan, including treatment for the environment and other pets in the family.
Mange is caused by a tiny, microscopic mite. Infestation with mange mites can cause intense inflammation and itching of the skin, with significant hair loss and scabby, crusty skin. Both Sarcoptes and Demodectes mites are difficult to eliminate and require an intense treatment program over several weeks.
Fungal infections, especially ringworm, are very common in puppies and kittens, especially those from farms, rescue programs and city pounds. Severe infections may require oral medications to resolve the problem.
Just like their human owners, dogs and cats commonly suffer from allergies. As with humans, pets may be allergic to almost anything. This may include air-borne substances such as plant pollen and dust, certain foods, soaps, cleaning agents, dust mites, plant material such as straw or wood chips, and other bedding materials. It is common for the allergy to cause skin inflammation and itching. Severe cases can be complicated by secondary bacterial infections. Flea allergies are also very common. Some dogs are so allergic, that one flea can make them absolutely miserable.
If the root cause of the allergy can be determined, removal of the source is often successful. Sometimes it is very difficult to determine the cause of the allergic reaction and the pet has to be treated symptomatically with medications to ease the inflammation response.
Some types of skin problems, especially hair loss may be caused by thyroid disease or other metabolic disorders. These typically need laboratory testing to confirm or properly test.