Are you sure the smell is from his hair and not his mouth? He easily could have decaying teeth which is causing the smell! It smells like a sewer
I have seen dogs with rotten teeth at 6 months of age. What color are his teeth on the side of his mouth. If it is yellow or green you need to get to your vet so he can clean his teeth. If decaying teeth are left untreated it can lead to infection in the dog and eventually cause heart problems and even death. Even if the vet has to pull his teeth it is not the end of the world, I have one with 3 teeth left and she still eats kibble. Very seldom do mine crunch their kibble but just eat it up.