Your vet will need to look for the cause of alopecia in your dog. As fleas are a common cause of dogs’ itchy skin and resulting hair loss, your vet may recommend a flea treatment (which you are hopefully up to date with already). Your vet may also take samples of hair or scrape a little sample of skin to test for ringworm and parasites, or take blood samples to look for underlying diseases such as hormonal problems – whatever is best for your dog.