Does your dog seem to be perennially scratching? Irritated skin, especially around the tail area? It may be that your canine friend is playing host to fleas, but it can also be an allergic reaction to food, and something akin to human's hay fever. According to a vet from South Louisiana:

Breeds that appear the most susceptible include terriers, miniature schnauzers, Dalmatians, setters, Lhasa apsos, bull dogs, pugs and breeds with narrow or squat snouts.

Common allergies include atopic dermatitis, flea, food, contact and bacterial. However, it's difficult for area physicians to pinpoint which are the most common.

If your dog has fleas, it's still technically allergy anyway. Not to the fleas, per se, but to the saliva of the fleas. And because flea bites are itchy, the skin irritation is exacerbated when the dogs scratch, or bite on the skin, which may then cause secondary bacterial infection. Flea collars will not work in this case, and shampoos and other flea control products may give temporary reprieve.

For long-term treatment, see your vet for your pet's allergy treatment options.