This is a total and complete guess, but the same *exact* thing happens to my cat when she gets flea bite dermatitis, i.e. skin allergies. What you describe is exactly what happens to her--and I know humans and cats are different, but, both are susceptible to skin allergens. Have you changed your diet--introduced new foods? New detergent, new shampoo or soap, new hair products? Something new in your environment like air freshener that might produce something you're allergic to in the air you're exposed to frequently? Or maybe new sheets / pillow cases that haven't yet been washed and may have carried something in from the store/factory?