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Polymorphous Light Eruption – Sun Allergy Polymorphous Light Eruption – Sun Allergy
by Kimberly Allen, RN For many of us spring and summer are a time for us to get outside and enjoy the warm weather... Polymorphous Light Eruption – Sun Allergy

by Kimberly Allen, RN

For many of us spring and summer are a time for us to get outside and enjoy the warm weather and sunshine.  However, for approximately 45 million Americans they are so hypersensitive to the ultra violet rays of the sun that even very brief periods in the sun can cause misery.  Polymorphous light eruption or PMLE is the most common type of idiopathic photodermatosis, or sun allergy.  PMLE affects approximately 10% to 20% of Americans, however, most experts believe it is more prevalent than estimated as many people do not seek treatment or report their symptoms to their doctor.  PMLE tends to occur more often in females than males.  Although PMLE can develop at any age it usually manifests in young adults.  It can affect people of all ethnicities as well as skin types, though it does affect people with fair skin more often.  PMLE also tends to manifest in people that live in northern climates than those that live in tropical climates.  Some experts believe that people that live near the equator gradually become desensitized to the sun’s harsh ultra violet rays.

PMLE is a sun allergy, a reaction by your immune system that is triggered by the changes that occur when your skin is exposed to the sun.  The exact reason why the immune system reacts as though  skin exposed to the sun is a “foreign” body, however, there is some evidence indicating there may be a genetic component.

People with PMLE develop an itchy rash on skin exposed to the sun.  The rash usually appears anytime from minutes to hours after exposure to the sun, sometimes it may not appear for a couple of days after exposure.  The rash usually appears as clusters of small red bumps or red, raised rough areas with itching and burning, and in some cases blistering and swelling.  The rash usually appears on the areas of your body that are not exposed to the sun during the winter but are exposed in the summer like your chest and back.  These symptoms most commonly appear in spring and summer.  Some people with PMLE become less sensitive to the sunlight as they are repeatedly exposed to the sun and though they may be somewhat desensitized through the  summer it almost always returns the next spring as soon as you start spending more time outside.  There are several conditions that can cause similar rashes so it’s important to note when your rash occurs report to your doctor if your rash is widespread and painful as well as accompanied by a fever.sun allergy

In most cases the rash tends to resolve on its own in a few days to a week.  For mild cases your doctor may recommend applying cool compresses to the rash areas as well as over the counter creams with hydrocortisone or over the counter antihistamines like chlorpheniramine or diphenhydramine.  If your symptoms are more severe your doctor may prescribe a stronger oral antihistamine and/or prescription strength corticosteroid cream.  In some cases the doctor may prescribe phototherapy which desensitizes your skin by exposing you skin to ultra violet light while at your doctor’s office.  Usually these treatments are given five times a week for three weeks.  If standard treatment fails your doctor may recommend antimalarial drugs or beta carotene tablets.

The best way to prevent symptoms of your sun allergy from developing is to apply a strong broad spectrum sun screen with an SPF of at least 20 or higher.  Limit your time outside between 10:00AM and 3:00PM when the suns rays are the strongest.  Always wear sunglasses that have ultra violet protection and a wide brimmed hat.  You should also wear light weight long pants and long sleeved shirts.  It’s also important to be aware that there are certain medications that can also trigger a photoallergic reaction.  If you are taking any medications that can contribute to PMLE ask your doctor if there is an alternative medication that could be used that would be effective yet not increase your sensitivity to the sun.

Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at