Flea bite dermatitis

When a flea bites your dog, proteins (antigens) in the insect’s saliva can cause an immune system reaction — the release of immunoglobulin that in turn causes itching.

Depending on the type of cell involved (mast cells, basophils, or T-lymphocytes in the blood) and the type of chemicals released, the irritation can begin immediately, in five-to-six hours or in 24-48 hours or a combination of the three — all from a single bite.

Small red raised bumps on the base of the tail and along the outside of the back legs, self-induced scratches, and thickened skin on the base of the tail are all signs of chronic flea allergy. The diagnosis can be confirmed with an intradermal skin allergy test at your vet’s.

Again, use your own judgement. You know your pet best, and should always be on the lookout for changes in skin, coat, or behavior. If you also have seen fleas, then chances are your dog has a flea allergy.