Sunburn is caused by overexposure to the sun's UV rays
(or those of a tanning bed) which cause the skin to become red, warm
and tender to the touch. A more serious sunburn can include extreme
redness, swelling and blisters and may be accompanied by nausea or
chills. Most sunburns appear 1 to 24 hours following intensive exposure,
and last for up to three days.