Database of diseases - Allergy

 

An example case - describing the phototoxic action of the sun on the skin:

A middle-aged woman received a popular antibiotic - pefloxacin - due to a urinary tract infection. During the treatment she spent a few hours in the sun. As a result of tanning, after a few hours, urticaria resembled sunburn.

Drug-induced urticaria caused by ultraviolet (UV) radiation may appear in the exposed areas - on the face, neck, and forearms. In this case, increased erythema occurred, combined with edema. Symptoms were accompanied by severe pruritus and burning. The symptoms lasted for several days. A specialist doctor, who was notified by a patient concerned about the severity of symptoms and their chronicity - said photodermatosis.

Phototoxic UV rays - they cause photodermatoses

 

Among the diseases caused by sunlight, attention is drawn to dangerous diseases called photodermatoses. Their symptoms are skin changes, for example, urticaria appearing all over the body. These changes may be accompanied by burning and itching, which in extreme, very rare cases can be difficult to bear. That this is not an abstract disease is shown by a tragic departure years ago - Hannelore Kohl, wife of the former Federal Chancellor of Germany, about whom all media wrote about him.

Why can the sun be harmful?

Contrary to popular beliefs, the sun works badly on the skin. It causes premature aging, increased risk of skin cancer, photodermatosis, urticaria, solar changes, etc. The reason is the solar ultraviolet, which consists of three types of radiation - UVA, UVB and UVC. UVA rays are harmful because they can reach even the subcutaneous layer and damage its cells. UVB rays allow the synthesis of vitamin D3 necessary for the construction and regeneration of bones, but are also responsible for skin burns and skin cancer. Ultraviolet UVC radiation should not reach the ground, it protects against ozone layer. Unfortunately, the risk of penetration of UVC rays increases, as the phenomenon of so-called ozone hole. This radiation is carcinogenic and lethal to life.


Sun rays falling on the skin can trigger reactions:

- phototoxic
- photoallergic.


Phototoxic reactions

Phototoxic reactions occur when after absorbing light energy through the skin (mainly UVA) - foreign chemical substances present in its tissues are photoactivated. These substances are primarily some of the components of the drugs that we use orally, cosmetics that we apply to the skin, some herbal and vegetable substances from foods, sometimes these are substances produced as a result of diseases or metabolic disorders produced by our own body. These photoactivatives, giving the body's energy to light, release toxic free radicals. This causes damage to the skin cells and acute inflammation. Symptoms of skin lesions and lesions include erythema, edema, urticaria, blisters, eczema, etc. This reaction is usually limited to the place where both these factors simultaneously act - i.e., light radiation and the presence of a phototoxic substance.


Phototoxic reactions - allergy to sunlight

The mechanism of sensitization to sunlight is as follows - under the influence of light energy present in the body, the above-mentioned photoactive substances (from foods, medicines, cosmetics, etc.) - turn into allergens! These are quite new substances that are formed by combining with the proteins of skin cells.The longer or shorter solar exposure will now be sustained to trigger a defensive reaction of the immune system that confuses photoallergic reactions with germs. The result is acute local inflammation of the skin that causes urticaria and swelling.


Where are the most common skin lesions under the influence of the sun?
 
Skin changes are usually limited to exposed sites, and therefore - face, neck, cleavage, hands, shins. But be careful! The sun's rays can also penetrate through clothing.


Ed. Edward Ozga Michalski, MA
Consultation by prof. dr hab. med. Andrzej Danysz
 

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