|Might be just a co-incidence? Now, I'm about 4 days into this fleece insert thing, so I am by no means an expert. But unless your son has an allergy to what fleece is made out of(which I would think would mean a rash wherever the fleece touches him, not just on the end of his penis), I can't see why it would be the fleece. Every once in a while my boy gets a sore on the end of his penis too, it's something that doesn't happen often and seems to come from no where. I just be sure to wipe him down after every diaper change and put a big glob of Aquafor on it. A couple of diaper changes later, it's gone. I don't think it's yeast as I haven't ever used yeast creme and it still goes away. It's almost like it's a contact sore or something. My older son gets one underneath his penis sometimes in the winter and he wears undies. So, at least in my case, it seems to be a contact sore and not caused by fungus or an allergy or their skin just not liking a certain kind of material against it. That's my experience anyway.