The chemicals (chlorine/fluoride) used to treat your water or bacteria in the water could be a possible cause. A change in soaps/detergents could produce such a reaction. Dust mites, molds, mildews, and other airborne allergens could be a factor as well. Do you know if your water is treated; and if so, what chemicals are used to treat it?
Because your skin's moisture barrier is depleted, you will need to address this problem with a natural moisturizer. Your skin is an external organ and will need to be addressed both internally and externally. You can take a visit to your local Whole Foods Market for natural skin care product selection. The Shikai brand of products may be a good choice for you. In particular, the moisturizing bath/shower gel and the Borage Skin Therapy Lotion (fragrance free).