A couple of possibilities. Dry skin is often a sign of a deficiency in essential fatty acids. There are several ways to tackle this. You can take flax or hemp seed oil, borage oil, Twin Labs cod liver oil skin formula, and/or fish oil. You can try adding fatty fish to your diet, such as wild salmon (not farmed) or sardines or talapia (again, wild, not farmed), and/or fatty seeds such as ground up flax or hemp. You might also consider adding lecithin to your diet. As for shampoo, a good natural shampoo rich in essential fats, such as made by a company like Aubrey, shouldn't be a problem, and it helps to clean out the surface bacteria that can also cause itchy scalp. Conditioners are much more of a problem than gentle, natural shampoo. Shea butter is great for lips, but it rubs off quickly, so that could be part of that problem. Dr. Bronner's makes a good organic lip balm that has shea butter in it that won't wipe off so often. As for the mouth blisters, that sounds like it could be your toothpaste. Check to see if it has sodium laurel sulfate in it (this has many spellings). If it does, find one that doesn't. That might clear up that problem. You can find them in a good health food store.
I have very dry skin and scalp too. I have to carry a chapstick and hand lotion with me wherever I go and use it on a frequent basis, otherwise I have the same happen.