Hello and thank you for asking your question. My name isXXXXX will try to help.

One of the most common causes is folliculitis. It is an infection of, and inflammation of, the hair follicles. It can occur even if you do not see any redness or itching. The treatment would be oral antibiotics, for infection, and possibly cortisone for inflammation.

He should also be tested for "demodex mange." Demodex is always present on the skin. Certain dogs react to it which causes hair loss. It can be diagnosed by scraping some cells from the top layer of the skin. This is then examined under the microscope. Treatment is ivermectin or related products.

He could also have ringworm which is a fungal infection.This would be diagnosed by plucking a few hairs, from an affected area, and putting them on a special growth gel to see if they grow fungus. It can be treated with topical and oral medication.

I would rule these out first as they are the most common. If you can get the inflammation under control, hopefully the hair will grow in black.

He could also have vitiligo. This is where the melanocytes, that produce pigment, die or no longer function. It can be diagnosed with a skin biopsy. Unfortunately there is not treatment for it.

Hypothyroidism, where they thyroid gland does not produce enough thyroxine, can cause hair loss and coat color changes as well. This is seen more often as they get older so it is lower on my list of differentials. It is diagnosed with a blood test and treated with a daily thyroid supplement.

I hope this helps.

If you have additional questions, please click "reply." Many Thanks