I have a 4month old and he tends to scratch alot. My vet told me it could well just be a habit! Not sure if this helps you..
Ours was scratching a lot. Noticed that when we put front line on him, within a week he started scratching. Skipped the next month and most of itching gone.
Use a shampoo with aloe and oatmeal. That's what I use on my tri colour. I use a whitening shampoo on my tuxedo (black and white)
My darling girl is 10 years old. She has had itchy skin for most of her life. I got special shampoo from the vet with cortizone in it and a cortizone leave in conditioner that helped. Much later we realized her particular problem was also an auto-immune disorder which she now takes steroids to correct. If it is allergies, using oatmeal based shampoo or the ones from the vet help a lot. Also ask your vet about giving benedryl or other antihistimines.
After changing foods several times, trying every possible shampoo and conditioner, and buying expensive fish oil capsules that she won't touch! I have found if I give her about 1/2 a can of tuna in oil every week or so her hair is shiny, her skin doesn't appear to be dry and scaly anymore and the itching and scratching is all but gone. My sweet girl used to scratch her hair off in spots and she appeared sore...poor thing! I felt so bad, she is much better now I highly reccomend the tuna. Good luck.