AnnaFalkDVM has good advice. I would also give the dog a distilled vinegar water bath because it is soothing to the skin and isn't harsh like soaps.
A dog can scratch itself due to many reasons like to mention a few liver disease, lice, fungus, fleas or anxiety. However the most common cause is allergies and it tends to get worse as the dog gets older. Among mammals, dogs and cats are the pets most frequently seen with allergies. To relieve the itching sensation, dogs may scratch and bite themselves or rub their face with their paws and other objects.
Unfortunately there is no permanent remedy for the condition and in the words of a veterinarian "are a lifelong problem", however there are some treatments to relieve the itch and cure infections and scars as a result of constant scratching, and even "desensitize" a pet to substances that cause allergies.
The reasons for allergies could be numerous like they could be due to fleas, the food they eat, airborne particles in the air they breathe in, or allergies due to physically touching something. We should find the key to the dog's itchiness and make it comfortable. Determining the reason of allergies will give us a key to solve the problem.
They may scratch because they have some sort of dry skin condition. You could try to get a shampoo that is moister rich and conditioner too. Also when you bathe the dog try to make sure all the soap is off there fur and skin before you dry them this may cause skin irritation as well good luck.
He may have ticks or fleas, check him for this and get him a collar if it isn't he may have some type of rash, get him checked out at the vet
If your dog doesn't have flees, I would check into a food supplement from Dinovite. My friend uses a supplement from Dinovite for her boxer and she rarely scratches now.
My poppy keep scratching n biting , should I give her a piriton tablet ? Now
' but later we will be getting her some flea treatment just in case its fleas. Poppy is I year old now !
Yeah that could be the cause you should trying looking at what you feed her and clean her at least 2 times a week..! Hope I helped and sorry if I didn't hope she gets well soon..!