
My now deceased foundation bitch had hot spots on occasions. They tended to occurring the summer and my Vet suspected it was flea allergy that set them of, even though she never showed signs of having fleas. We started using Frontline spray every three months and she never was troubled by them again.
They did not seem o coincide with her being bred from (she had two litters) and actually most of hers occurred after she was spayed.
One or two of the others of her five generations of descendants have ha the occasional hot spot (two I think) and they were entire, adn in those teh hot spots were results of injury to the skin due to rough play and the weather being humid and a secondary yeast/fungal infection setting in where the skin had been damaged.