If you break out in a rash after spending time outside, the cause might not be bug bites or plants you touched.

You may have a sun allergy, Marshfield Clinic dermatologist Dr. Clayton Green said.

A sun allergy causes different symptoms than the redness, pain and peeling of a sunburn. Some people get a rash or hives when their skin is exposed to the sun’s rays.

Rashes caused by the sun

There are two main types of rashes caused by sun allergies.

1) Polymorphous light eruption, or PMLE, is a rash that looks like a large number of mosquito bites. The rash is most intense in late spring when the weather starts getting sunnier, but tends to improve over the summer.

“It’s very itchy, uncomfortable and a major nuisance,” Green said.

The bumps can be treated with a steroid cream, but the best way to stay rash-free is to use sun protection.

2) Solar urticaria, or hives caused by the sun, is less common than PMLE but can be more serious.

The condition can cause an anaphylactic reaction – which cuts off the ability to breathe — to the sun in severe cases, Green said.

People who experience mild solar urticaria can avoid a reaction by using sun protection, but people who have severe reactions should stay indoors when it’s sunny.

If you think you have a sun allergy, you should see a dermatologist. [button-seafoam url=”https://marshfieldclinic.org/Doctors/Search?k=dermatology” target=”_self” position=”center”]Find a dermatologist[/button-seafoam]

Sun allergies caused by connective tissue diseases

Certain connective tissue diseases cause skin reactions to the sun. Two of these diseases are dermatomyositis, which involves skin and muscle inflammation, and lupus.

Sun exposure can worsen skin lesions common among people who have lupus and dermatomyositis.

In some cases, patients are so sensitive to the sun that a bad sunburn will cause an immune system reaction that damages internal organs, Green said.

Medications can cause skin reactions

Some medications can cause skin reactions to the sun. While you won’t get a rash that’s typical of a sun allergy, you could end up with a bad sunburn.

Doxycycline, an antibiotic commonly used to treat Lyme disease; Benadryl; and the prescription acne treatment Accutane make the skin more susceptible to sunburn, Green said.

Avoid sun allergy symptoms

Not surprisingly, common sun protection methods are the best way to stop a sun allergy from flaring up.

• Wear long sleeves, pants, a hat and sunglasses.
• Stay in the shade.
• Stay indoors during the hottest part of the day, between 10 a.m. and 2 p.m.
• Use sunscreen with a physical blocker like zinc oxide or titanium dioxide.
• Reapply sunscreen each time you get out of the water or dry off with a towel, or every hour if you’re sweating.

Green suggests using sun protection even if you don’t have a sun allergy.

“Skin cancer is much more common than sun allergies,” he said.

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