Allergy > Understanding Allergy > Types of Allergy > Types of Sun Allergies

Common Types of Sun Allergies

When a person exhibits unfavorable signs and symptoms after the body is exposed to a harmless agent in the environment, a hypersensitivity reaction occurs. Sun allergy is a form of an immediate hypersensitivity reaction which is classified as Type 1. All hypersensitivity reactions are manifestations of immune system disorders.

When the body is exposed to an allergen, white blood cells specifically the mast cells and the basophils invade to the site where an allergen is found. Inflammatory process begins due to extreme vasodilation and influx of fluids and blood in the area, causing pain and itchiness due to prostaglandins. 

Sun allergies take into form when a person is exposed to the sun and his or her immune system responds to it in an abnormally over-reactive way. Sun allergies are most often triggered by sudden environmental alterations to which the skin is exposed. Studies regarding the concrete and specific pathophysiology of this disorder are yet to be definite. The etiology specifically would be a person’s exposure to sunlight in conjunction with other hypersensitivity problems and problems regarding the immune system. The defense system of the body, hypothetically, reacts after the first initial interaction of the skin against the sunlight. The cells of the sun-exposed skin are altered. These alterations are the gradient to the rising hyperactivity response of the body.

Sun allergies take the form of rashes, most commonly. Sun allergy is also a form of eczema, which is a long term, non contagious disease of the skin as a manifestation of hypersensitivity to allergens in which the skin has direct contact to. Eczema is also termed as contact dermatitis. When these eczema-like rashes are further irritated due to hand contact or other environmental allergens, or when they are scratched, further skin eruptions occur. Macules, papules, pustules, scars and crusts may form. Blisters may also form as a manifestation of fluid influx along with other defense factors in the area. Sites of allergies are very prone to scars, making the skin in the area very fragile to injuries.

Sun allergies can be triggered when exposed to the sunlight in just a few minutes. The differentiation between people who have this allergy and those who don’t is still unknown. Persons with histories of allergy in any form, mostly bronchial asthma, are the ones most bothered by sun allergy. The higher rate of prevalence shows that heredity is the most common factor.

Sun allergies are further classified to smaller types. Some of these types are the following:

1) Actinic Prurigo

These forms of allergy are also called hereditary Polymorphous Light Eruption. People of Indian ethnicities are the most common victims of this allergy whether they be from the central, north, or south America. The symptoms often start and appear during childhood to adolescent years. In persons who have this allergy, a comprehensive assessment of heredofamilial history should be obtained. Genetics is the most common factor why persons have this allergy. It may be passed to a number of generations from one ancestry. The rashes are mostly facial extending to the neck. The symptoms of actinic prurigo are mostly similar to that of the classic PMLE, though they are more intense and they appear earlier. Actinic prurigo is also seasonal as of PMLE. Although in countries with tropical climates, the symptoms may persist all year round. Treatments for actinic prurigo include prescription-strength corticosteroids to reduce inflammation, PUVA, beta carotene, and thalidomide.

2) Polymorphous light eruption (PMLE).

PMLE is one of the most common forms of sun allergies affecting people. It usually appears after a person has obtained sunburn. It appears as an itchy, irritating rash in reddened skin exposed to the sun’s ultraviolet rays. In some cases, skin eruptions turn to tiny fluid-filled blisters or as thickened reddish plaques in the skin. PMLE may also appear as bleeding-like areas under the skin. Body parts commonly affected by PMLE include the neck, upper and lower extremities, and the upper chest. A person with PMLE may also experience one to two hours of headache, nausea, body malaise and chills. It does not choose any ethnicity, place of residence, or heredity. Prevalence on women is higher though, compared than in men. Symptoms initially appear during adolescent to young adult years as compared to actinic prurigo that appears during childhood. This type of allergy is also seasonal, since it does not appear much during cold climates such as winter. Warm environments trigger the appearance of the skin lesions which often appears during the summer and spring. The exposure to the sun is more often by these times compared to winter in which persons decide to spend time indoors. Gradual desensitization may treat PMLE but it does not have a universal effect. Some persons tend to become more sensitive to sunlight when exposed for longer periods of time. When desensitization is achieved, PMLE sometimes recurs when warm climates return. PMLE produces a rash within an hour or two of sunlight exposure. Its rashes are often generalized. Hyperthermia may be present along with body pain after its onset. PMLE rashes though can subside within two or three days if sun exposure is avoided.

For mild symptoms, PMLE can be managed through cold compresses to decreases vasodilation and inflammation. A damp cloth is applied on areas with rashes or water can be sprayed over the area. Oral antihistamines are mostly prescribed by dermatologists such as diphenhydramine or chlorpheniramine. Cortisone cream can also be applied topically to relieve the itching. For more severe symptoms, dermatologists usually prescribe stronger antihistamines and topical corticosteroid creams. If the patient is not responding to the medication, the physician might advise phototherapy, which is a way of gradually desensitizing the patient through increasing doses of ultraviolet rays. This procedure is done in the clinic supervised by a doctor. Beta carotene tablets are also prescribed in these cases.

3) Photoallergic eruption.

A person with no direct sun allergies might be the ones affected by this kind of allergy. Photoallergic eruption is a form of delayed hypersensitivity.  Chemicals applied on the skin act as mediators to trigger allergic reaction and appearance of skin lesions. It it’s the reaction of sunlight with the topical chemicals that irritates the skin, not the sun alone.  Orally taken drugs may also cause this type of allergy since its components go to the bloodstream, and then to the skin. An ingredient in sunscreens, topical antibiotic treatments, perfumes and cosmetics trigger this kind of allergy. Drugs with profound side effects or those that requires prescriptions have common adverse effects involving this allergy. Oral antibiotics and psychiatric medications, oral contraceptives and hypertensive drugs tend to trigger skin allergies as their adverse effects. Some cyclo-oxygenase inhibitors, analgesics and antiulcerants also trigger this form of allergy. This form of allergy is often delayed and occurs around 1-3 days of sun exposure. Photoallergic eruptions are usually seen as read rashes or small fluid-filled blisters. The skin lesions may extend even to skin covered by clothing. They may appear around one to two days of sun exposure. Usually, the usage of the chemical or the drug is stopped to allow the allergy to heal. The aim of the treatment is to determine the causative chemical triggering the hypersensitivity reaction. Corticosteroid topical creams are usually prescribed to heal the rashes.

4) Solar urticaria.

This form of allergy appears immediately after sun exposure. Its rashes are large and very itchy. It is very rare though and mostly affects women. Hives are usually seen on uncovered skin parts that may be exposed to sunlight. It may appear just after minutes following sun exposure. Usually, skin lesions fade within 30 minutes to one hour. For mild symptoms, an oral antihistamine drug can be taken. Anti-itch topical creams with cortisone can also be applied to site. Severe cases may require stronger antihistamines and corticosteroid topical creams. Doctors may also advise phototherapy to gradually desensitize the patient.