Sun Allergy:  When Ultraviolet is Ultra-Itchy
Posted by:  Audrey Kunin, M.D.  (DERMAdoctor) 

You might think you’re allergic to the sun. Why else would the sun-exposed parts of your body break into a rash every spring, when sunlight starts to become more intense? 
Well, most so-called cases of sun allergy really aren’t a true allergy, in which the immune system reacts to an allergen like pollen. Rather, they are a hypersensitivity to the sun, called Polymorphous Light Eruption (PMLE). 
This condition is most commonly seen in parts of the world that have 4 seasons and it’s most commonly triggered by springtime sun exposure. The rash only forms on sun-exposed parts of the body, usually 1 to 4 days after exposure. The sensitivity of the skin and the severity of the rash gradually lessen as spring changes into summer and the skin becomes adjusted to ultraviolet rays. 
There is nothing specific about the rash caused by PMLE. Red blotches appear that may be raised, bumpy or hive-like. 
Polymorphous Light Eruption affects women and men; , and adults and children, equally. However, the problem typically begins between the ages of 20 and 35. (Native Americans have a high rate of PMLE and there is some evidence of a genetic predisposition.) 

An Accurate Diagnosis 

Because the rash is so nonspecific, its presence limited to only on sun-exposed areas is a very important diagnostic feature. sparing of areas out of reach from sunlight like skin folds, jawline and below the chin also help sleuth out the diagnosis. 

Ruling Out Autoimmune Disease 
A rash triggered by sunlight is not a guarantee of polymorphous light eruption. Patients with autoimmune diseases (like lupus and many others), often have heightened sun sensitivity. 
When I work-up a sun-induced rash, I always rule out the possibility of an autoimmune disease masquerading as PMLE. 
A simple blood test called an ANA (antinuclear antibody test) helps determine the true diagnosis. A positive ANA test does not always indicate autoimmune disease; many healthy people do test positive. A true positive ANA result shows significantly elevated levels of ANA and has proper “pattern” as recognized by the lab. The definitive diagnosis of autoimmune disease requires more detailed testing and the patient must meet other specific disease criteria. 

A Skin Biopsy 
The patient who doesn’t improve as the summer progresses may want to pursue a more in-depth work-up. a skin biopsy might be in order to confirm the diagnosis of PMLE. What might be going on? Perhaps the ANA was normal but an autoimmune disease is present nonetheless. Perhaps it’s another skin disorder mimicking PMLE. It’s time to find out. 
If your sun-induced rash doesn’t get better as spring changes to summer, ask your doctor about a skin biopsy. Make certain the doctor intends to order a second test on the tissue, called a DIF (Direct Immunofluorescence). This is an essential test whenever an autoimmune disease is even remotely considered in the diagnosis. The dermatologist must a special fixative for DIF on hand to place the specimen into. At the time of biopsy, don’t presume; it’s better to ask. 

Light Testing 
In difficult to diagnose cases, light testing provides a useful option. An area of unaffected skin is exposed to a medical ultraviolet b light. Approximately 3 out of 4 people with PMLE will respond to the light exposure with a rash. 

Treating PMLE 
Itching is the main symptom that PMLE patients complain of. 
Oral antihistamines like OTC Benadryl or prescription Atarax (hydroxyzine) are effective medications to control the itching. 
Other OTC remedies for soothing discomfort include anti-itch preparations like Sarnol-HC 1%, PrameGel, Caladryl Clear Lotion and Aveeno Oatmeal Anti-itch Concentrated Lotion. 
Topical steroid creams also help reduce itching and can hasten resolution of the rash. Prescription strength cortisone creams are more potent and effective. non-prescription 1% hydrocortisone cream, Cortaid Steroid Cream - is a useful home treatment, particularly when PMLE strikes you unprepared. 
Unresponsive, prolonged or severe forms of pmle may require Plaquenil (hydroxychloroquine) or Atabrine (quinacrine). These mediations used in the prevention and treatment of malaria, have been used with great success in PMLE. Therapy may vary. For some it may be used on a limited basis; such as during a vacation in a sunny clime; for others, it may be a year-round necessity. 
The use of medical-grade ultraviolet light (UVA and/or UVB) provides another treatment option. Called “hardening,” this form of desensitizing light exposure helps patients who are very sensitive to seasonal fluctuations in sunlight stay comfortable. Risks surrounding UV light exposure (skin cancer, premature skin aging and cataracts), make it vital to precisely control exposure and monitor for future problems. In other words, it’s not a treatment you should try on your own at the local tanning salon. 

Sun Protection 
Sun protection is important for everybody—but it’s uniquely important for those with chronic PMLE. 
Use a sunblock that has both UVA- and UVB-blockers with a high SPF. Total Block Clear SPF 65 and Total Block Cover-Up/Make-Up SPF 60 are great products that completely block both UVA and UVB, as well as infrared and visible light rays. 
Treat clothing with Rit Sun Guard Laundry Treatment UV Protectant. Add it to your washing machine along with the laundry detergent. It boosts the ultraviolet protection factor of normal cloth from 4 to 30! A wide brimmed hat is also a smart choice. 
Should you find yourself with an odd little “sun allergy” you simply can’t explain — consider the possibility of PMLE.

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