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Sun allergy: causes, types, treatment


Sunlight can trigger the body’s immune response. It’s called photosensitivity or sun allergy.   

This condition is characterized by the appearance of an itchy rash. Skin exposed to sunlight may develop reddened or inflamed areas. But the specific symptoms and course of the disease may differ depending on the type and cause of the reaction.

Conditions of photosensitivity include solar urticaria, chemical photosensitivity, and polymorphic eruptions caused by light. As a rule, the tendency to all of these reactions is hereditary. But certain diseases can also lead to them. For example, systemic lupus erythematosus and some porphyrias. They can cause more severe cutaneous manifestations.  


Of all the photosensitivity reactions, the most common is light-induced polymorphic eruption (PVSS). For example, in the United States, 10-15% of the population suffers from this condition. 

This is a reaction primarily to UVA light. Therefore, it can be provoked not only by the sun, but also by ultraviolet radiation in the solarium. Why PVSS arises is still not fully understood. But it is known that women who live in a northern climate and are regularly exposed to the sun most often suffer from PVSS. Often, this reaction first appears in adolescence or in the second decade of life. The likelihood of this condition occurring after 30-40 years is much lower.  

You can recognize PVSS by an itchy rash that looks like multiple red bumps and irregular, red, raised areas (the so-called plaques). Less commonly, blisters.

Typically, areas of the skin are affected, such as the chest and shoulders, which are exposed with the arrival of heat. But on the hands and face, which are exposed to the sun all year round, a rash almost never occurs.

Most often, symptoms show themselves within 30 minutes to several hours after you have been in the sun. But sometimes the reaction develops with a delay of several days. It usually appears after the first influence of the warm spring sun and lasts for several days. But it can arise again – after the next exposure to the sun. Further, if exposure to the sun becomes constant, the rash is reduced by reducing sensitivity to ultraviolet light.

A type of PVSS is a juvenile spring rash. According to one theory, sunny, but, at the same time, cool weather leads to it. Typically, the rash appears on the ears. Children, especially boys, most often suffer from this problem. This is due to short, boyish hairstyles that do not cover the ears.  


Like PVSS, solar urticaria may appear with the first warm rays of the sun. It presents as large, itchy red bumps or sores. 

This allergy to the sun is rare and appears a few minutes after exposure to the sun. Like PVSS, solar urticaria most commonly affects young women and weakens as exposure to the sun increases.

The average age at the time of the first outbreak is 35 years. But it can occur at any age, even in newborns.

The manifestations of the disease can vary from mild to severe – up to anaphylactic shock. This is a life-threatening allergic reaction.

If the skin lesions are too large, the following may also be added to the skin symptoms:

· Headache and wheezing,      

· Dizziness,      

· weakness      

· Nausea.      

A type of sun allergy is pruritus or actinic itching . It manifests itself as itchy rashes in the form of nodules or plaques that also occur after sun exposure. This problem, which is hereditary, affects mainly the indigenous peoples of the American continent and the Caucasians. For the first time, symptoms of the disease can appear in childhood. 

Quite often, this disease manifests itself as lip inflammation.


Patients with allergic contact dermatitis may develop chronic actinic dermatitis over time In this case, sunlight can lead to the appearance of eczematous papules and plaques. They have a fairly clear contour of manifestation along the clothing line. Typically, this disease affects older men.  


More than 100 substances, when applied to the skin, taken by mouth or injected, can cause reactions when exposed to the sun. This is called chemical photosensitivity. This sensitivity is of two types: phototoxicity and photoallergy.   

These reactions may resemble a lumpy rash or sunburn.

Phototoxicity is more common than photoallergies and can cause long-term damage to the skin. 

This reaction occurs when a drug or chemical compound absorbs sunlight and forms substances that cause inflammation.

With phototoxicity, people experience pain and redness, inflammation, and sometimes brown or blue-gray discoloration of skin areas that have been exposed to sunlight for a short time.

These symptoms are similar to those of sunburn. But the reaction differs from sunburn in that it only occurs after a person has swallowed certain drugs (such as tetracycline or diuretics) or chemical compounds. Or I applied them to the skin (for example, perfume and coal tar). Several plants (including lime, celery, and parsley) contain furocoumarins. These compounds make some people’s skin more sensitive to UV light. This is called phytophotodermatitis. 

All phototoxic reactions appear only on those areas of the skin that have been exposed to the sun. They usually develop within hours of exposure to ultraviolet light.

Have you applied a cream or ointment to your skin, went out into the sun and after a while (sometimes several days) notice redness, peeling, itching, and sometimes blisters and spots? This may be a photoallergic reaction . It occurs when a product applied to the skin reacts to sunlight.  

That is, sunlight turns the agent into an allergen.

As UV light hits certain compounds, it changes their molecular structure. The result is the formation of small molecules called haptens that trigger an immune response.

Usually, symptoms become noticeable 24 to 72 hours after sun exposure.

Photoallergies are not limited to areas exposed to sunlight and can spread throughout the body.

This type of reaction can be caused by aftershave lotions, sunscreens, and sulfonamides.

Photoallergies can be caused by:

· Drugs against anxiety (alprazolam, chlordiazepoxide);      

· Antibiotics (ciprofloxacin, doxycycline, levofloxacin, ofloxacin, tetracycline, trimethoprim);      

· Antidepressants (tricyclic antidepressants);      

· Antifungal medications that are taken orally (griseofulvin);      

· Antigiperglikemiki (antidiabetic drugs);      

· Sulfonyl urea;      

· Antimalarials (chloroquine, quinine);      

· Antipsychotics;      

· Phenothiazines;      

· Drugs for chemotherapy (dacarbazine, fluorouracil, methotrexate, vinblastine);      

· Diuretics;      

· Thiazides;      

· Preparations for the treatment of acne (taken by mouth);      

· Medicine for the heart (amiodarone, quinidine);      

· Drugs for pain relief (analgesics);      

· NSAID (especially piroxicam and ketoprofen);      

· Skin products;      

· Antibacterial agents (such as chlorhexidine and hexachlorophene);      

· Coal tar;      

· Flavors.      


There are no specific tests for photosensitivity reactions. A doctor may suspect a photosensitivity reaction when the rash appears only in areas exposed to sunlight. Careful examination, examination of medical history, skin symptoms, medical conditions and drugs taken by mouth, or substances that are applied to the skin (such as drugs or cosmetics) can help the doctor determine the cause of the photosensitivity reaction. Doctors can do tests to rule out conditions that make some people susceptible to these reactions. For example, by diagnosing the aforementioned systemic lupus erythematosus.

When a rash develops on an area of ​​skin that has been exposed to the sun and the diagnosis is clear, doctors may do mimicking tests (ultraviolet light provocation) or photo tests. These tests can help figure out what type of photosensitivity reaction might be causing it.    


If you are sensitive to the sun, it is best not to go outside when it is too active. If this is not possible, use a sunscreen with a physical blocker such as zinc oxide or titanium dioxide. It blocks UVA and UVB rays more effectively than a chemical blocker sunscreen. It is also advisable to wear long sleeves and hats.    

If possible, after consulting a doctor, you should stop using any drugs or chemicals that may cause photosensitivity. To treat chemical reactions to photosensitivity, corticosteroids are applied to the skin and avoid substances that cause the reaction.

Solar urticaria can be difficult to cure. However, doctors can also try antihistamines, corticosteroids, or sunscreens for this. If these treatments fail, you can try ultraviolet light therapy. Its goal is to gradually develop a tolerance for sunlight through deliberate exposure to ultraviolet light. This therapy starts with a very low UV level that rises over time.

People with PVSS or photosensitivity due to systemic lupus erythematosus may receive symptom relief from topical corticosteroids or oral hydroxychloroquine. The latter is an antimalarial drug that is often used in dermatology.

Phototherapy can also have beneficial effects.

It will not hurt to take vitamin D for the formation and maintenance of the protective ability of the skin.

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