The vet nurse in me said fleas first of all - not glad to know that you have a flea but glad to know my mind was sharp for a change! I can remember Wallis doing that - screaming bloody murder because of a flea bite. Fortunately she doesn't have the allergy problems with the fleas that Tibby does. Fleas like lighter colored dogs best, so she usually gets more on her, Sasha next and Tibby last.
We have an appt on Wednesday to have the growth in Wallis's anal gland checked - this is with a different vet. I wish I'd known of the pumpkin years ago because she has always had issues back there. I just got a "recipe" for treats that are dehydrated sweet potato that I may try. Better than rawhide!!
In case the vet didn't tell Josh, a flea spends 98% of its time in the environment and not on the dog. So you may need to consider treating other dogs and the house. It's cold there so they've all found rides into the warm house!
RIP Wallis, John Robert, Tibby & Pip
Mom to JoJo, Roxie & Linguini (Cavaliers)
and my birds Moji (Senegal) and Walter (Blue Front Amazon)