Definition
A sun allergy is usually understood to be a skin reaction caused by excessive sunlight (UV radiation), which can take place in different forms and requires different treatment.
Causes
The term sun allergy covers many symptoms and reactions of the body to light, UV and heat radiation. One of the most common skin rashes caused by the sun is the so-called polymorphic light dermatosis, which can best be attributed to the umbrella term sun allergy. It is also called solar eczema and is more common in women than in men.
Adolescents and young adults are particularly frequently affected. There are many theories as to the exact mechanism of origin of a sun allergy. However, this has not yet been exactly proven.
The main trigger is believed to be sunlight, which irradiates the unprotected surface of the skin for several hours. Afterwards it is assumed that the body releases endogenous substances, the exact origin of which is not yet known. These substances then stimulate the body’s immune system.
The immune system then forms IgE-type proteins that bind these messenger substances. The reason is that these endogenous substances are first recognized as foreign and therefore the immune reaction starts. As soon as the body’s own substances are bound by IgE, mast cells dock to the complex and histamine is released.
This then triggers the symptoms typical of allergies. Histamine leads to a constriction of the bronchial tubes (rather insignificant in the case of sun allergies) and to a dilatation of the blood vessels and a resulting increased flow of blood. This ultimately leads to the well-known reddening of the skin.
Furthermore, there are also forms of sun allergy that only occur through the combination of sunlight and certain medications or foods that were taken at the time of exposure to the sun. One substance frequently mentioned in this context is St. John’s wort, which, when taken over a long period of time, is suspected of triggering unpleasant skin reactions when exposed to the sun at the same time. Skin reactions caused by certain substances in connection with sunlight exposure are also called phototoxic reactions.
The mechanism of formation is complicated and involves the emission of various chemical substances and intermediates. A rare special form of light and sun allergy is the so-called xeroderma pigmentosis, in which even the slightest exposure to sun and light can lead to blistering of the skin. Affected patients usually have to spend their entire lives in darkened rooms and avoid sunlight completely.
This is quite possible, even if the composition of the radiation in a tanning studio differs from normal sunlight. The radiation contains more UV-A and less UV-B radiation but both types of radiation can cause a sun allergy. Again and again one reads that the prophylactic attendance of the Solarium can prevent a sun allergy.
However, this is only true to a limited extent. The sense of this tip is that the body gets slowly accustomed to the UV radiation. Whether this happens in the Solarium or in the spring sun, is in the final effect insignificant. One can carry a sun allergy off both by sun and by the radiation in the Solarium. It is therefore important to increase the dose slowly to prevent the occurrence of a sun allergy.
