Itching and irritation are often caused by eating foods that you are allergic to. You don't have to have classic allergy symptoms to have an allergy; often allergic reaction happen hours after eating the allergenic substance and you might not even feel it. Try elimenating the common allergens milk, soy, wheat, dairy, eggs, and peanuts from your diet for 3 weeks and see if it helps. My son and I used to have have a lot of irritation and itching around our nose and cheeks and also on the arms and legs, but it went away after we were tested for hidden food allergies and went off the foods we were found to be allergic to. Wheat and milk are especially known for causing itching and irritation.