Pathogenesis (development of disease)
Dermatitis solaris describes an inflammatory reaction of the skin caused by an overdose of sun exposure or artificial UV light. It usually involves UVA, but UVB and UVC rays can in principle also lead to sunburn. Damage to the epidermis occurs. As a result, various inflammatory mediators are released, which in turn trigger dermal inflammation (inflammation of the dermis). UVA radiation (wavelength: 320-400 nm) UVA radiation is a long-wave, low-energy radiation that causes rapid tanning. These rays are filtered by the skin only to a small extent, which means that they penetrate deep into the skin and attack the elastic fibers (collagens). About 55% penetrate into the epidermis and about 40% into the dermis. In contrast to sunburn, the resulting cell damage (oxidative damage to DNA including double-strand breaks) is neither visible nor noticeable. For this reason, frequent exposure to UV-A radiation results in premature skin aging (skin dryness, pigmentary changes) and wrinkling (incl. elastosis) as well as an increased risk of skin cancer (see below secondary diseases). Studies in recent years have also shown that not only natural radiation from the sun, but also artificial light sources, such as those found in solariums (UVA high-power lamps), contribute to carcinogenesis (cancer development). Consequently, the World Health Organization (WHO) has already classified UV radiation as a class 1 carcinogen.
UVB radiation (wavelength: 280-320 nm) UVB radiation is a short-wave, high-energy radiation that causes slower tanning. A large part of these rays are blocked by the horny layer of the skin. Another part penetrates into the epidermis. Due to its energy, UVB radiation is able to break the double strands of DNA and cause lasting damage to the skin. UVB radiation is responsible for tanning the skin, but also for sunburn, which is dangerous to health (risk of skin cancer). UVC radiation (wavelength: 200-280 nm) UVC radiation is a very short-wave, high-energy radiation. It is practically completely absorbed by the keratinized skin already at the surface and is therefore less effective in damaging deeper cell layers than UVB light, which is absorbed more weakly and thus penetrates to the deeper cell layers. The biological effect of UVC rays is damage to nucleic acids. The best-known representative of nucleic acids is deoxyribonucleic acid (DNA), the storehouse of genetic information. In addition to their role as information stores, nucleic acids can also serve as messengers (signal transducers) or catalyze biochemical reactions.
Etiology (causes)
Biographic causes
- Skin type – fair-skinned people of skin type I and II are very often affected.
Behavioral causes
- Long stay in the sun or artificial UV light.