
moist dermatitis
The initial cause may be an insect bite a scratch, then if there is dampness and warmth it allow either bacterial or fungal infection. there is a cycle of self trauma and the body reacting with an inflammatory response and the area oozes. Yuk.
I have them just appear in humid hot weather, whether there was any insect involvement I couldn't say but they have occurred at the time when fleas are most plentiful, though none have been found on the dog.
I have also had them occur when another dog has grabbed at it's fellow in over rough play and obviously caused a small wound, which has turned into a hot spot.
With my bred I am always desperate to limit hairloss, as it can take until the next moult to grow back the same colour, not good if your showing and the dog looks moth eaten.