What is sun allergy?
A sun allergy is a condition that happens when the immune system reacts to sunlight.
The immune system treats sun-altered skin as foreign cells, leading to the reactions. The reactions that can occur include a rash, blisters or hives. Only people with sensitivity to the sun will exhibit symptoms. For some, the reaction could occur after only a few moments of exposure to the sun.
Sun allergies are fairly common although they are often not reported.
What are types of sun allergy?
There are several types of sun allergy. These include:
- Actinic prurigo: This is an inherited version of sun allergy. Symptoms are stronger than other types and it is common among Native American populations, although it affect all races, including Caucasians. Symptoms can begin in childhood.
- Photoallergic reaction: This type occurs when a chemical applied to the skin reacts with sunlight. Several types of medications, as well as sunscreens, cosmetics, and fragrances can cause the reaction. Symptoms sometimes do not show for two to three days.
- Polymorphyic light eruption (PMLE): This is the most common form of sun allergy. About 10% to 15% of the U.S. population is affected. It occurs more in women than men and usually starts in their teens and twenties. PMLE is usually seen as a rash that causes itching and can appear as blisters or small reddened areas. Most cases occur during the spring. Symptoms usually appear a few hours after exposure to the sun.
- Solar urticaria: This sun allergy is rare and produces hives. Hives can appear only after a few minutes of sun exposure. It mostly affects young women. Symptoms can be mild or severe to the point of anaphylactic shock (a life-threatening allergic reaction).
Symptoms and Causes
What are the symptoms of sun allergy?
- Actinic prurigo: This usually presents as very itchy crusted bumps (nodules).
- PMLE and photoallergic reaction: A burning or itchy rash and fluid-filled blisters are common. The rash is often seen within two hours of exposure to the sun.
- Solar urticaria: Hives occur in minutes for people with this reaction. Burning and a sensation of stinging may occur at first. The rash fades over days to weeks. In some cases, the skin may darken after the reaction.
Sun allergy is mostly seen in spring and early summer. With continued exposure to sun during summer months, the skin “hardens” and the likelihood of developing sun allergy diminishes.
What parts of the body are most affected by sun allergy?
While a sun allergy reaction can occur anywhere on the body, it is most commonly seen on parts of the body exposed to the sun: arms, legs, hands, and the back of the neck.
In severe cases of sun allergy, even areas protected by clothing may be affected. Interestingly, areas of the skin that are normally exposed to the sun (such as face and back of the hands) are usually spared from sun allergy.
What causes sun allergy?
The cause is not known exactly. Some forms of sun allergy can be inherited, however.
Some medications can cause skin sensitivity, such as:
- Chemotherapy medications.
- Cardiac drugs.
- Drugs for diabetes,
Diagnosis and Tests
How is sun allergy diagnosed?
Your provider will look at your skin and take a medical and family history in order to make the diagnosis. In some cases, you might have other tests. These could include blood tests, phototesting or a skin biopsy.
In addition to diagnosing skin allergy, these tests will help rule out other skin problems, such as eczema and lupus.
Management and Treatment
How is sun allergy managed and treated?
- Seek shade during the hours between 10 a.m. and 4 p.m., the hours of maximum sun exposure.
- Use sunscreen, particularly a type that is SPF 30 or greater, is broad spectrum (protecting against UVA and UVB) and resistant to water.
- Keep the affected areas moistened to help with some symptoms.
- Check any medications you use to see if they cause photosensitivity.
- Consult with a dermatologist to help determine the best course of treatment for your sun allergies.