Photosensitivity is the most common type of reaction to the sun. It is not a true allergy. Photosensitive individuals often develop a rash because of a strong sensitivity to sunlight. In rarer cases, an individual will be sensitive to indirect sunlight or even fluorescent indoor lights. Certain medications or topical creams can increase the skin’s susceptibility to sunlight in these individuals.

Photoallergic eruption is an allergic reaction to a combination of an ingested or applied chemical to the skin, and sunlight. Some medications cause people to become sensitized to the sun and experience allergic reactions after taking the drugs and being exposed to sunlight. Other triggers of photoallergic eruption are lotions or medications that are applied to the skin followed by exposure to the sun. It is the combination of ultraviolet rays (an invisible form of radiation) from the sun and the chemicals in the substances that trigger the allergic reaction.

There are many medications that may cause sun sensitization in certain individuals, including:

• Birth control pills
• Antibiotics
• Antihistamines
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Antidepressants
• Herbal remedies (e.g., St. John’s Wort)
• Cold medications
• Blood pressure medications

Other triggers include:

• Cosmetics
• Perfumes
• Plants
• Sunscreen

The symptoms of photosensitivity/photoallergic eruption include an itchy, red rash or tiny blisters. In some cases, the rash may spread to skin covered by clothing. Symptoms may not appear until one or two days after exposure and will usually disappear after the problem chemical/medication is identified and its use is discontinued.

A combination of covering the skin while in the sun and using sunscreen will help prevent the occurrence of rashes in sensitive individuals. However, sunscreen should not be used if it is an allergen capable of causing a photoallergic eruption.

Some serious diseases (e.g., lupus, porphyrias) cause extreme sun sensitivity. For patients with these diseases, it is essential to avoid sun exposure as much as possible.