Polymorphous Light Eruption: Top Treatment & Prevention Strategies Revealed!

Polymorphous light eruption (PMLE), also known as polymorphic light eruption, prurigo aestivalis, sun allergy, sun poisoning, summer eruption/prurigo, or eczema solare, is the most common skin condition caused by sunlight. It is an allergic reaction to sunlight or other sources of ultraviolet (UV) light. A European study revealed that PMLE affects as much as 18 percent of the population. The condition usually manifests as an irritated rash that appears hours to days after exposure to direct sunlight. PMLE is generally treatable with both home remedies and medical interventions.

Understanding Polymorphous Light Eruption

PMLE is a delayed hypersensitivity reaction in the skin to unknown endogenous cutaneous photo-induced antigens. This abnormal response to ultraviolet (UV) light means affected patients develop an inflammatory response to an endogenous photo-induced antigen. UV radiation usually creates an immunosuppressive response in the skin, however, patients with PMLE may have a reduction in this normal response. In PMLE patients, UV radiation leads to an increased amount of CD4 and CD8 T lymphocytes, and an increased inflammatory response in the epidermis and dermis.

Symptoms of PMLE

Symptoms of PMLE usually begin within a few hours to days after sunlight exposure, typically in the spring or early summer. An itchy rash will appear on areas that were newly exposed to the light, including the décolletage (low neckline), chest, forearms, backs of your hands, lower legs, and feet. The rash usually doesn’t affect the face. While the rash varies from person to person, the particular rash you get will typically be similar every time it happens. Polymorphous means “many forms,” and PMLE can look different for different people. In rare cases, PMLE causes additional symptoms, like fever, headaches, and malaise. In general, symptoms of PMLE last for two to three days. Repeated UV light exposure while the rash is present may cause it to last longer.

Causes and Risk Factors

The exact cause of PMLE isn’t known, but genetics are thought to play a role. Experts have suggested it may also be at least partly associated with hormones, such as estrogen, low vitamin D, and factors within your microbiome. While the causes of PMLE are still under investigation, the rash is brought on by UV light. It’s important to note that, while UVA exposure is the typical cause, the rash can be a result of UVA or UVB exposure. This means that glass windows won’t provide enough protection from the sun to prevent a PMLE reaction. PMLE is not contagious. PMLE is about four times more common in women than in men. You might start feeling the symptoms at any age, but it typically begins in ages 20 to 40. It also occurs more frequently in places that are at higher altitudes and in more temperate climates.

PMLE often occurs in the spring when sunny weather returns. PMLE affects all ages, sexes, races and ethnicities. It’s most common among women, people between the ages of 20 and 40, those with a family history of PMLE, and people who live where sun exposure is uncommon. It’s possible that UV radiation alters a compound in your skin and your immune system reacts to the new compound. Both ultraviolet and occasionally visible light cause PMLE. Ultraviolet light has two types: UVA and UVB. UVB can damage your skin, but UVA penetrates deeper into your skin’s layers. UVA causes up to 9 in 10 cases of polymorphous light eruption. The rash can appear following sun exposure or from other sources such as tanning beds.

Diagnosis of PMLE

PMLE is usually diagnosed based on its symptoms, primarily the appearance of the rash when it occurs, where it’s located, and how quickly it heals. A clinical diagnosis of polymorphic light eruption can be made based on a history of a pruritic eruption occurring following sun exposure and previous episodes in spring or summer. To exclude other photosensitive conditions a skin biopsy may be considered. A skin biopsy might be taken in order to confirm the diagnosis, but this is not always necessary. Blood tests might also be used to rule out other conditions. In some cases, a doctor might expose a small part of your skin to UV light in order to confirm PMLE.

Your healthcare professional can probably make a diagnosis of polymorphous light eruption based on a physical exam and your answers to questions. You might undergo laboratory tests in order to confirm a diagnosis or rule out other conditions. Tests may include:

Skin biopsy: You may need a biopsy of the rash. A biopsy is a procedure to remove a sample of tissue for testing in a lab.
Blood tests: A member of your care team draws blood for testing in a lab.
Phototesting: A specialist in skin conditions (dermatologist) exposes small areas of your skin to measured amounts of ultraviolet A (UVA) and ultraviolet B (UVB) light to try to reproduce the problem. If your skin reacts to ultraviolet (UV) radiation, you're considered sensitive to sunlight (photosensitive) and may have polymorphous light eruption or another light-induced disorder.

Your healthcare professional might need to rule out other disorders characterized by light-induced skin reactions. These conditions include chemical photosensitivity, solar urticaria, and lupus rash.

Treatment Options for PMLE

If you avoid UV light, your rash will heal on its own in a few days to weeks. It won’t leave any scarring. After the rash has already appeared, a doctor may prescribe corticosteroids to help alleviate itchiness or burning. Other medications that might be used to treat PMLE include oral steroids, hydroxychloroquine, polypodium leucotomos extract, lycopene, nicotinamide, beta carotene, astaxanthin, and canthaxanthin.

Treatment of polymorphous light eruption often isn't needed because the rash usually goes away on its own within 10 days. If your symptoms are severe, your healthcare professional may prescribe anti-itch medicine (a corticosteroid cream or pill).

Read also: At-Home Red Light Therapy Devices

Medical Treatments

Corticosteroids: After the rash has already appeared, a doctor may prescribe corticosteroids to help alleviate itchiness or burning.
Other medications: Other medications that might be used to treat PMLE include oral steroids, hydroxychloroquine, polypodium leucotomos extract, lycopene, nicotinamide, beta carotene, astaxanthin, and canthaxanthin.
Phototherapy: Dermatologists can expose you to UV light a few times per week before the sun becomes strong in the spring to help avoid severe PMLE. This should only be done by a professional. This typically has to be repeated after every winter. Your healthcare professional may suggest phototherapy to prevent seasonal episodes of polymorphous light eruption if you have disabling symptoms. This exposes the skin to small doses of UVA or UVB light that helps your skin be less sensitive to light. A course may also be administered in early spring as a preventive treatment to induce skin tolerance for more severe PLE. The mechanisms by which phototherapy induces subsequent protection from the sun are likely to be through cutaneous immunosuppression. The carcinogenic potential of PUVA is well known. In people treated with PUVA for psoriasis the incidence of skin cancer (squamous cell carcinoma and melanoma) is significantly increased and this risk persists, and indeed continues to increase, with the passage of time after treatment. BBUVB is also associated with increased photocarcinogenicity in people with psoriasis, and animal studies suggest that NBUVB may be associated with twice this risk. Thus, the risk of skin cancer and also the time, cost and inconvenience involved in the treatment, have to be weighed against the benefits of ultraviolet therapy.

Self-Care Measures

Apply anti-itch cream: Try a nonprescription anti-itch cream, which may include products containing at least 1% hydrocortisone.
Take antihistamines: If itching is a problem, oral antihistamines may help.
Use cold compresses: Apply a towel dampened with cool tap water to the affected skin. Or take a cool bath.
Leave blisters alone: To speed healing and avoid infection, leave blisters intact. If needed, you can lightly cover blisters with gauze.
Take a pain reliever: A nonprescription pain medicine may help reduce inflammation and pain.

The Phenomenon of Hardening

The effect is not fully understood, but PMLE can undergo a process called hardening. This means that, as you’re exposed to UV light, your skin can build up a UV tolerance. Your first eruption of the year may be the most severe, with following eruptions progressively subtler. Gradual hardening is one form of treating PMLE. This can be done through careful and measured exposure to sunlight, or it can be achieved through the use of phototherapy.

There is a phenomenon called the skin hardening effect where chronic exposure to sunlight leads to skin changes including increased melanin and thickening of the stratum corneum. These changes are thought to restore the skin’s normal immunosuppressive response to UV light and hence reducing or resolving PMLE over time.

Prevention Strategies for PMLE

To reduce the effects of PMLE, the American Academy of Dermatology (AAD) recommends seeking shade and applying sunscreen. If you can, avoid the sun when it’s at its strongest during the middle of the day. Experts recommend using sunscreen that’s SPF 50, broad spectrum (meaning it blocks both UVA and UVB rays), and water-resistant. You should reapply every 2 hours. Additionally, the AAD suggests covering your skin from direct sun exposure. There are many clothing choices that can help you do this, such as dense fabrics, dark or bright colors, long-sleeve shirts and pants, wraparound sunglasses with UV protection, wide-brimmed hats that cover your head, neck, and ears, and shoes that fully cover your feet.

Protecting your skin from the sun can help prevent PMLE symptoms:

Avoid sun exposure during hours of peak sun ray intensity.
Use sunscreen. Sun protection with broad spectrum sunblock that works against UVA rays is important.
Apply generous amounts of sunscreen with a sun protection factor (SPF) of at least 30. Pay special attention to your face, nose, ears, neck, shoulders and hands.
Apply sunscreen 30 minutes before sun exposure so that it has time to penetrate the skin.

To help prevent symptoms of a sun allergy, you must protect your skin from exposure to sunlight. Use a sunblock on your lips. Be aware of skin care products and medicines, especially certain antibiotics, that may trigger a photoallergic eruption.

Protect the rash from further sun exposure: When you go outside, cover the area where the rash developed. Because the sun's rays are most intense during this time, try to schedule outdoor activities for other times of the day.
Use sunscreen: Fifteen minutes before going outdoors, apply a broad-spectrum sunscreen, one that provides protection from both UVA and UVB light. Use a sunscreen with a sun protection factor (SPF) of at least 30. Apply sunscreen generously, and reapply every two hours - or more often if you're swimming or perspiring. If you're using a spray sunscreen, be sure to cover the entire area completely.
Cover up: For protection from the sun, wear tightly woven clothing that covers your arms and legs. Consider wearing a broad-brimmed hat, which provides more protection than does a cap or visor. Consider wearing clothing designed to provide sun protection. Look for clothes labeled with an ultraviolet protection factor (UPF) of 40 to 50. Follow care instructions on the label of UV-blocking clothes to maintain their protective feature.

Living with PMLE

There aren’t any severe physical complications strongly associated with PMLE, but a severe case of the condition may lead to emotional distress, anxiety, and depression. If you have PMLE and you find that it’s affecting your well-being, a healthcare professional can advise you on appropriate strategies to manage these feelings.

If you have a sun allergy, the outlook is usually very good, especially if you consistently use sunscreens and protective clothing. Of all forms of sun allergy, solar urticaria is the one that is most likely to be a long-term problem.

Additional Tips for Managing PMLE

Check Vitamin D Levels: People who avoid sun exposure may be at risk of low levels of vitamin D. They should think about checking their serum vitamin D levels and consider taking vitamin D supplements of 10-25 micrograms per day or consuming more foods rich in vitamin D.
Nicotinamide: Using oral or topical antioxidants as well as oral nicotinamide prior or after the first sun exposure has shown to prevent PMLE.
Desensitisation Treatment: If very troublesome, desensitisation treatment may be considered. Desensitisation is a way of raising the skin’s resistance by treating it with increasing doses of ultraviolet light in a special phototherapy cubicle. The treatment is given in the early spring so that the skin is ready to cope with the summer sun.

When to Seek Medical Advice

If you have an unexplained rash, you should make an appointment with a primary care physician or dermatologist. A rash can be a symptom of many different conditions. If you have a rash in addition to other symptoms that are more serious, you may need emergency care. If in doubt, call a doctor.

Seek immediate medical care if your rash is widespread, is painful, or comes with a fever.

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