The sun. A vitamin or a poison?

Sausis 10, 2020

The sun. A vitamin or a poison?


Sunlight has a positive effect on a person's health, well-being and performance, but it can also cause a wide range of skin problems, from mild flushing to cancer, and often provokes sun allergies or photodermatoses.

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Photodermatoses are skin diseases caused or provoked by the sun's ultraviolet rays (mainly UVA). They are more common in women and people with lighter skin types. There are up to 30 different types of photodermatoses in the literature, but the most common are polymorphic light eruption and solar urticaria.

Solar urticaria

Solar urticaria is a rare (~0.08% of all urticaria cases) but severe photodermatosis. It is characterised by redness, itching, and a rash similar to a sting. “This is a true sun allergy because when exposed to UV rays, the skin undergoes various immune reactions: it produces photoallergens, which, after repeated exposure to UV rays, bind to mast cells and cause the characteristic rashes. In severe cases, when a large area of skin is affected, a life-threatening allergic reaction — anaphylactic shock — can occur,” Malvina Baikštienė, a doctor at the Centre for Innovative Dermatology, says. Hives and itching are more pronounced in areas exposed to UV rays, but can also occur on areas of the body covered by clothing, as UVA rays can also penetrate the barrier of some textiles. Rashes disappear within 24 hours if the sun is avoided, and if they persist for longer than that, it is not an allergy, but a so-called polymorphic light eruption.

Polymorphic light eruption

Polymorphic light eruption is the most common photodermatosis, with a prevalence of ~10–20% in Central Europe, Scandinavia, and the USA. Although the exact pathogenesis of this disease is not entirely clear, it is thought to be a slow-type hypersensitivity reaction to photoallergens produced in the skin when exposed to UV rays. As its name suggests, this dermatosis is characterised by a variety of rashes, including spots, papules, nodules, plaques, and vesicles, but on an individual basis, each patient tends to have one type of rash, which is always accompanied by severe itching.

“This dermatosis usually appears in spring or early summer, when we get a lot of sunlight after winter. Skin lesions appear a few hours or days after exposure to UV rays, most often on the face, neck, décolleté, arms and legs,” explains dermatovenerologist Professor Matilda Bylaitė-Bučinskienė. As summer progresses, this dermatosis diminishes or disappears, and sometimes sun tolerance develops, but the rashes recur every year. Sometimes, after many years, spontaneous improvement or even complete disappearance of this dermatosis is possible.

How are harmful sunlight “kisses” treated?

Sun-induced dermatoses are suspected by examining the skin, listening to the patient's complaints, and identifying an association with the sunny season, exposure to the sun and itchy rashes on exposed areas of the body. Blood tests are carried out if other skin or systemic internal diseases (lupus erythematosus, blood diseases, etc.) are suspected. To confirm a diagnosis of photodermatosis, a photoprovocation test is performed with different doses of UV light on the skin.

Although the skin lesions usually resolve themselves within a few hours (in the case of solar urticaria) or days (in the case of polymorphous light urticaria), without leaving any signs, the unpleasant symptoms mentioned above can have a negative impact on your quality of life, such as interfering with the enjoyment of your holidays and other pleasurable activities, etc. In addition to all the standard protective measures — proper SPF50+ sunscreen, goggles and tightly woven clothing — local or systemic corticosteroids and antihistamines are commonly prescribed to control these photodermatoses. “The most effective preventive measure to avoid these dermatoses is pre-treatment with UVA or UVB rays — phototherapy 3–4 times a week. 4–6 weeks before anticipated UV exposure or holidays. To ensure minimal exposure to UV rays, preventive radiation is only administered under specialised medical care and not in tanning salons,” says Bylaitė-Bučinskienė, the founder of the Innovative Dermatology Centre.

Preventive measures

If you have a sun allergy or hypersensitivity to the sun, here are some tips to help you avoid symptoms:

·       Limit exposure to the sun, especially when it is at its most active (10 a.m.–3 p.m.)

·       Avoid sudden exposure to sunlight. Gradually increase your exposure to the outdoors to give your skin cells time to adapt to sunlight. You should start enjoying direct sunlight from 15 to 20 minutes per day.

·       Sunglasses, long-sleeved clothing, and a wide-brimmed hat help protect your skin from UV rays.

·   Use sunscreen. Choose a broad-spectrum sunscreen (UVA and UVB) with an SPF of at least 30 and preferably SPF 50+. It is recommended to apply it every 2 hours. &

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