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Sun Allergy (Photosensitivity)

Medically reviewed by Last updated on Dec 25, 2023.

What Is It?

Harvard Health Publishing

A sun allergy is an immune system reaction to sunlight, most often, an itchy red rash. The medical term for this condition is Polymorphous Light Eruption (PMLE). The most common locations include the "V" of the neck, the back of the hands, the outside surface of the arms and the lower legs. In rare cases, the skin reaction may be more severe, producing hives or small blisters that may even spread to skin in clothed areas.  

Sun allergies are triggered by changes that occur in sun-exposed skin. It is not clear why the body develops this reaction. However, the immune system recognizes some components of the sun-altered skin as "foreign," and the body activates its immune defenses against them. This produces an allergic reaction that takes the form of a rash, tiny blisters or, rarely, some other type of skin eruption.  

Sun allergies occur only in certain sensitive people, and in some cases, they can be triggered by only a few brief moments of sun exposure. Some forms of sun allergy are inherited.  

A few of the most common types of sun allergy are: 


Symptoms vary, depending on the specific type of sun allergy:

Solar urticaria — Hives usually appear on uncovered skin within minutes of exposure to sunlight.


If you have mild symptoms of PMLE, you may be able to diagnose the problem yourself by asking yourself the following questions:  

If you can answer "yes" to all of these questions, then you may have mild PMLE.  

If you have more severe sun-related symptoms — especially hives, blisters or small areas of bleeding under the skin — your doctor will need to make the diagnosis. In most cases, your doctor can confirm that you have PMLE or actinic prurigo based on your symptoms, your medical history, family history (especially American Indian ancestry) and a simple examination of your skin. Sometimes, additional tests may be necessary, including:  

If you have symptoms of a photoallergic eruption, the diagnosis may take some detective work. Your doctor will begin by reviewing your current medicines as well as any skin lotions, sunscreens or colognes you use. The doctor may suggest that you temporarily switch to an alternate medication or eliminate certain skin care products to see whether this makes your skin symptoms subside. If necessary, your doctor will refer you to a dermatologist, a doctor who specializes in skin disorders. The dermatologist may do photopatch testing, a diagnostic procedure that exposes a small area of your skin to a combination of both ultraviolet light and a small amount of test chemical, usually a medicine or ingredient in a skin care product.  

If you have symptoms of solar urticaria, your doctor may confirm the diagnosis by using photo-testing to reproduce your hives. 

Expected Duration

How long the reaction lasts depends on the type of sun allergy:


To help prevent symptoms of a sun allergy, you must protect your skin from exposure to sunlight. Try the following suggestions:  


If you have a sun allergy, your treatment must always begin with the strategies described in the Prevention section. These will reduce your sun exposure and prevent your symptoms from worsening. Other treatments depend on the specific type of sun allergy:

When To Call a Professional

Call your primary care doctor or a dermatologist if you have:

Call for emergency help immediately if you suddenly develop hives together with swelling around your eyes or lips, faintness or difficulty breathing or swallowing. These may be signs of a life-threatening allergic reaction.


If you have a sun allergy, the outlook is usually very good, especially if you consistently use sunscreens and protective clothing. Most people with PMLE or actinic prurigo improve significantly within five to seven years after diagnosis, and almost everyone with photoallergic eruption can be cured by avoiding the specific chemical that triggers the sun allergy.

Of all forms of sun allergy, solar urticaria is the one that is most likely to be a long-term problem. However, in some people the condition eventually subsides.

Additional Info

National Institute of Arthritis and Musculoskeletal and Skin Diseases

American Academy of Dermatology

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.