Dry skin can be hereditary but there are other causes that may exasperate it. A low-fat diet will increase dryness, low water intake and excessive UV exposure. Incorrect skin care can also dry skin out and it will also occur with a lack of essential fatty acids. Skin that is in a stressed, inflamed state can be caused by internal or hereditary factors, surface factors (such as a reaction to products applied, topical steroids, post laser treatment or surgery) or disease (eczema, asthma). As you age your skin also becomes more sensitive.