The appearance of skin affected by sun allergy can vary widely, depending on what's causing the problem. Signs and symptoms may include:

• Redness

• Itching or pain

• Tiny bumps that may merge into raised patches

• Scaling, crusting or bleeding

• Blisters or hives

Signs and symptoms usually occur only on skin that has been exposed to the sun and typically develop within minutes to hours after sun exposure.

Certain medications, chemicals and medical conditions can make the skin more sensitive to the sun. It isn't clear why some people have a sun allergy and others don't. Inherited traits may play a role.

Risk factors for having an allergic reaction to sunlight include:

• Race. Anyone can have a sun allergy, but certain sun allergies are more common in people with lighter skin.

• Exposure to certain substances. Some skin allergy symptoms are triggered when your skin is exposed to a substance and then to sunlight. Common substances responsible for this type of reaction include fragrances, disinfectants and even some chemicals used in sunscreens.

• Taking certain medications. A number of medications can make the skin sunburn more quickly — including tetracycline antibiotics, sulfa-based drugs and pain relievers, such as ketoprofen.

• Having another skin condition. Having dermatitis increases your risk of having a sun allergy.

• Having blood relatives with a sun allergy. You're more likely to have a sun allergy if you have a sibling or parent with a sun allergy.