While many day-to-day ailments can be cured with rest and fluids or a trip to the primary care doctor, when more serious illness rears its head a physician with specialized training and experience may be called for. All physicians share essential tasks, such as examining patients; taking medical histories; using tests to help make a diagnosis; and prescribing medications. They may counsel patients on healthy habits and how to keep well. Some physicians specialize in diagnosing and treating ailments in a particular organ or area of the body, a type of illness, or a mode of treatment, for example, Allergists and immunologists treat allergic diseases and those that affect the immune system. Dermatologists help patients with skin conditions. Neurologists specialize in diseases and disorders of the nervous system. Pathologists study the causes and nature of diseases. Radiologists use X-rays and radioactive materials to identify disease. Doctors of sports medicine help athletes prevent injuries, and treat those that occur during sporting events and training. Physicians and surgeons often have long, demanding workweeks. Unlike in primary care, the patients cared for by these specialists have already been referred because of their symptoms so they are often more ill, with more serious conditions. Physicians and surgeons have extensive education and training. After a bachelor’s degree, physicians earn a medical degree, which typically takes 4 years to complete, and then 3 to 7 years of internship and residency programs, depending on the specialty.