A sunburn is reddening of the skin that occurs after you are exposed to the sun or other ultraviolet light.

The first signs of a sunburn may not appear for a few hours. The full effect to your skin may not appear for 24 hours or longer. Possible symptoms include:

• Red, tender skin that is warm to touch.
• Blisters that develop hours to days later.
• Severe reactions (sometimes called "sun poisoning"), including fever, chills, nausea, or rash.
• Skin peeling on sunburned areas several days after the sunburn.

While the symptoms of sunburn are usually temporary (such as red skin that is painful to the touch), the skin damage is often permanent and can have serious long-term health effects, including skin cancer. By the time the skin starts to become painful and red, the damage has been done. The pain is worst between 6 and 48 hours after sun exposure.

In severe sunburns, blistering of the skin may occur. Deaths have resulted from acute sun exposure, and significant temporary disability is experienced by millions of sunburned people each year.

Sunburn results when the amount of exposure to the sun or other ultraviolet light source exceeds the ability of the body's protective pigment, melanin, to protect the skin. Sunburn in a very light-skinned person may occur in less than 15 minutes of midday sun exposure, while a dark-skinned person may tolerate the same exposure for hours.

Keep in mind:

• There is no such thing as a "healthy tan." Unprotected sun exposure causes premature aging of the skin.
• Sun exposure can cause first and second degree burns.
• Skin cancer usually appears in adulthood, but is caused by sun exposure and sunburns that began as early as childhood. You can help prevent skin cancer by protecting your skin and your children's skin from the harmful rays of the sun.

Factors that make sunburn more likely:

• Infants and children are especially sensitive to the burning effects of the sun.
• People with fair skin are more likely to get sunburn. But even dark and black skin can burn and should be protected.
• The sun's rays are strongest during the hours of 10:00 a.m. to 4:00 p.m. The sun's rays are also stronger at higher altitudes and lower latitudes (closer to the tropics). Reflection off water, sand, or snow can intensify the sun's burning rays.
• Sun lamps can cause severe sunburn.
• Some medications (such as the antibiotic doxycycline) can make you more susceptible to sunburn.