Heat or exposure to intense sunlight may result in dehydration and severe sunburns. Minor sunburns typically cause nothing more than slight redness and tenderness to the affected areas. There may be contributing factors of the wind to windburn, and similarly, sunburns. Common medical problems include food and waterborne diseases, insect bites, sunburns, heat stress/stroke, and dehydration. Sunburns associated with indoor tanning can be severe. In the skin it protects the cells from harmful UV radiation and prevents sunburns. Sunscreens are products commonly known by their capacity of protecting skin against sunburns. Sunburns may be classified as superficial, or partial thickness burns. People taking doxycycline should avoid sun exposure because of higher risk of sunburns. Sunburns and the development of cataracts in orcas in captivity are attributed to this exposure. Extreme sunburns can be painful to the point of debilitation and may require hospital care. Most sunburns heal completely within a few weeks. Studies have found that even serious sunburns could not affect sweat gland function and thermoregulation. Gradually developed tan in the spring prevents sunburns in the summer. The best treatment for most sunburns is time.