My dog is losing hair on his stomach and armpit. What's the cause?

There could be a couple of reasons why Diesel is losing hair on his stomach and armpit. He could have a skin infection causing the hair loss, or could be suffering from Cushing's disease. It could also be that he's very itchy. Severe itching can be caused by fleas, mites, ringworm, or allergies. If he isn't up to date on his flea treatment, I can give you one for him. First, I would give him Capstar. It's a one time pill that starts killing fleas within 30 minutes. Then follow up with a spot on treatment, such as Advantage or Revolution. This is a treatment that has to be used once a month. You will also have to disinfect the environment. Wash his bedding in hot soapy water, and vacuum the furniture and carpet surfaces. You can use a spray to kill fleas in the house, such as Indorex, or a flea bomb would work well to kill the fleas in the home.

If he is up to date on his flea treatment, I recommend taking him into the vet for an exam tomorrow. The vet can do blood tests, skin scrapings, and use a Wood's lamp to diagnose Cushing's disease allergies, mites, and ringworm. The vet can also check to see if he has a skin infection. Once the cause of the hair loss is found, the vet can prescribe the appropriate treatment. I would give your vet a call to set up an appointment. Best of luck, I hope this helps!