my 9 month old dog ryler and my 1 1/2 year old dog sparkey had fleas. we got them a flea collar and flea treatment ryler cant stop scratching his butt, i dont know i its an allergic reaction or somthing else. please help

Is it possible that he has worms?
Otherwise, I'd head to the vet.

I have to agree that a visit to your vet is in need. It could be a multitude of things, from blocked anal glands to a skin irritation. The vet is the only one that can tell you for sure, as both of these problems need drastically different treatments.

It definately could be many things. There is the possibility of worms or that his anal glands are blocked. There is also a possibility of mange. If he is developing a rash that may be a sign. Demodectic mange is actually very common in young dogs. Vet diagnosis with a skin scrape is the best bet.