The skin gets dry mostly because of the dry air. That is, the moisture of the skin vanishes due to it, thus, leaving it dry. Other reasons are extensive hot showers, certain soaps, medical conditions such as hormonal changes, psoriasis, diabetes, hypothyroidism, etc. Even malnutrition can cause the same as the body does not get all the required nutrients. Whereas oily skin is mostly a hereditary problem, however, it can also be caused due to hormonal imbalance, improper diet, cosmetics, and humid weather.