Dry skin is a symptom and not a disease. Patients with ichthyosis have dry, flaky skin, but dry, flaky skin is not necessarily a sign of ichthyosis. Dry skin can be caused by a variety of factors, including skin diseases such as ichthyosis and eczema, endocrine diseases such as hypothyroidism, nutritional and metabolic diseases such as vitamin A deficiency, and even excessively dry winter conditions.