There are many reason for hair loss. What are you feeding the dog? it could be a food alllergy.
here is an intteresting link to hair loss:
http://www.vetinfo4dogs.com/dhairloss.html
and here is one article from the link:
Hairloss
Question: I have a beagle mix whose hair has been comming out by the hands full for
the last 6 mos. We brush him often and we get gobs of hair off him. The
skin is very flacky under his hair
the hair loss is the worst on his back from the neck area to his tail. Some
of the hair did not grow back and the skin is very dark. We use advantage
for flea control. A thyroid test was negative. This problem seemed to come
on after a cortizone shot was given when he was chewing his front paw to
the bone. The paw cleared uand then the hair loss problem began. He also
scratches his rump on the furniture. I have read your article on seasonal
flank alopecia and it doesn't appear to be the same thing. Thank you for
making your web site available.
Answer: Harry-
Hairloss that occurs on the top of the dog and forms a triangle of
hairloss, with the widest part of the triangle at the base of the tail and
the point somewhere between the base of the tail and the shoulder blades,
is usually due to flea bite or mosquito bite hypersensitivity. Imidocloprid
(Advantage Rx) is a very good flea control product, so it seems somewhat
unlikely that flea bite allergy is the problem, unless you live in a place
where your beagle is exposed to new fleas on a continual basis or unless
there is a problem with the use of the product, such as too frequent
bathing, application of the wrong size of the medication or giving it
orally instead of applying it topically (yes, this last one is based on an
experience at our practice, so I know it can happen).
There are some conditions that can resemble flea allergy, including
hypersensitivity to anal sac secretions, food allergy and sometimes
inhalant allergies.
Almost all allergic conditions respond to corticosteroids, so it is odd
that the problems seemed to get worse after the injection. However, there
are times when a secondary bacterial infection is present and a cortisone
injection makes the situation a lot worse, instead of better. This may be
what happened in your beagle's case.
There are also times when the hair loss occurs due to hormonal disease.
These disorders are more common in older dogs, usually six years of age or
older. Hypothyroidism is the most common hormonal disorder leading to skin
problems so it made sense to check for that first. The next most common
problem is hyperadrenocorticism (Cushing's disease, HAC). Since this is a
disorder in which high natural cortisol levels are causing the hair loss
and skin irritation (if these signs are present), giving additional
cortisone might make the situation worse. I can't actually recall a case in
which this happened, though --- and just like most vets, I have given a
dog cortisone based on clinical signs resembling flea allergy that
eventually turned out to be Cushing's disease.
The other thing that sometimes resembles flea allergy is mange. In my area
Sarcoptic mange would be most likely to cause these problems but in some
areas of the country another mite, cheyletiella, might also cause similar
problems. Sarcoptic mange is very itchy and it can be really hard to find
the mites. So it is sometimes necessary just to treat for the mites in
order to figure out if they are there.
It can take several tries and several different test procedures to isolate
the cause of a skin condition. If your vet is unable to resolve the problem
after several visits, it might be a good idea to ask for referral to a
veterinary dermatologist. Most of the time, if you work with your vet and
you both are patient, skin problems can be resolved.
Mike Richards, DVM
9/19/2000