Sure it's not something you have done BUT Logi is very allergic to Dettol, we used to use the floor cleaner until Logi reacted badly on his left stifle, we think he laid down on a bit on the floor that I had not mopped up, it looked liked wet excema, that being said we didn't get tests done just process of elimination, I do think it looks like a flea allergy try combing him with a child's nit comb and see if you get any fleas or flea dirt. Calamine lotion will help soothe his tummy too.
What food is he on? I would think that the vet gave him both a steroid injection to stop the itching and antibiotic jab to stop it getting infected. Bless him, make sure the water is tepid and not too warm as it will soothe him, (I am sure you know most of this, just thinking out loud if you know what I mean)
It could of course be a heat rash have you had it rather warm where you are?
Bless him it does look sore give him a kiss from Grampy Logi bogi, Granny Leah and Great Granny Tarka x x x x x
