Examine the area, is the skin flaky? is the skin raw beneath the coat? Is the coat dry - meaning non-oily? do you bathe him regularly? If so are you using a shampoo that strips the coat of oils? Believe it or not you need only bathe your dog once a month and a Baby Shampoo (No tears, gentle formula) is the best bet. Unless your dog goes running through the mud, or rolls in grease a monthly bath is all you need to give - any more than that and you will strip the coat and skin of the natural oils.
Do you feed him people food? If not, do you just feed him dry kibbles?
You treated him for fleas, did he have fleas when you treated him? If not what kind of treatment did you use and Why? Was it a shampoo or was it the oil you put on their neck and shoulders? Mind don't treat for fleas until there are fleas - the stuff we use are insecticides. Not really a good thing putting poison on a person or pet.
Is he getting enough grease in his diet? Unlike humans greasy hair is a good thing when it comes to dogs who's skin requires a good deal of oils to maintain their health - Yes, it makes for a stinky mutt at times. However oily coats and skin is what dogs use for insulation from both heat and cold. Remember dogs don't sweat, thus oily skin/coat is their first defense from the elements.
Try about a 1/4 cup of bacon grease mixed with his kibble every other day for about say 2 weeks - see if this does anything. If there is a slight improvement, continue this kind of treatment, after about a month you should reduce to one greasy bowl of food per week or fortnight depending on the results. Short haired dogs require more greasy foods than long haired.
If it isn't just a dry skin issue it could be an allergy - To what? hard to tell. Perhaps that flea stuff?
If the skin is flaky it could be a form of dermatological disease that may need an ointment, or pills or shot. If the skin is raw that means it got damaged - if its not healing that means there is repeated damage - both need a Vet to look into for more ointments, pills and possibly a shot for infections.
If you are bathing regularly, stop it (No not you, him) yes I know he will start smelling like a dog - but he is a dog. DO NOT use flea and tic treatments until your dog/cat has fleas or ticks. Animals will get an allergic reaction to these at any old time - sure you can use it for a long time then suddenly the animal starts reacting to it.
Diet is always important. Folk figure you can feed a dog (or cat) dry food all of their life and they are good - That is like you eating one food all of your life, sooner or later something will go wrong. I suggest reading up on BARF - Bones and Raw Food Diet.
http://www.njboxers.com/faqs.htm Don't bother spending money on their book and dog foods, all of the stuff you have in your kitchen for you is pretty much in this diet.
Sugar (refined sugar) Chocolate and onions are a no no when it comes to dogs - all else - well they are omnivorous just like you and me.
Then use a mixture of people food and dog food. We keep a bowl of dry kibble down all the time for Sirius (our black lab) She gets scraps of food off our plates nearly every night, she will only eat about 2 cups of kibble per day she self regulates her diet. Dogs who are given only 2 cups of food and thats it will tend to gobble and eat all of their food at once - not good for the dog. Having a full bowl around at all times will lead to a change in the eating habits, such as noshing all day long. This may be another key element in your diet issue that is leading to dry skin, Kibbles are greasy, if the dog is only eating one huge meal once a day, then chances are he is getting a glut of grease at one time and the rest of the day no grease is flowing through the system.
Brewers yeast - A couple of tablespoons added to that bacon grease and kibble will go a long way at strengthen and improving the skin and coat - (We are talking a fairly big dog, not a toy puddle right?) Now you can run out tot eh pet supply store and get the Pills for your dog - but in reality getting it from the food store is far cheaper and just as good.
If not shampooing and the additions to the diet and the stopping of flea and tick treatments do not clear up the kin condition, they you can pretty much lay odds that the dog has attained a new allergy. Dogs will contract allergies through out their lives -
I think that just about covers it all.
cheers
David