Allergies caused on skin by sunlight
These conditions are less known compared with other disorders that are secondary to sunlight exposure such as sunburn and photocarcinogenesis. Most of these idiopathic photodermatoses emerge very early in life and are capable of altering significantly the quality of life of a kid. Finally we concentrate on the concept of photo protection with the goal of pointing out the importance of prevention in reference to sun exposition.
Adverse effects on skin derived from the exposition to sunlight have a high rate of worldwide incidence. The problem has a huge importance during childhood since it has been estimated that the maximum exposition to sunlight is done before eighteen years of age.
Cutaneous disorders which are not produced by the direct toxicity of the exposition to sunlight or photo allergic disorders represent a type of altered reactivity in the presence of ultraviolet radiation; among them the idiopathic photodermatoses have a very importance place given their prevalence. Many of them start at childhood and are capable of altering significantly the quality of life of a child. The main handling is general terms preventive and includes education, change of behavior in the presence of sunlight, the use of appropriate clothes and an adequate use of sunscreens.
The modern obsession of exposing to sunlight has a great incidence of the fact that secondary effects have become more frequent on daily practice. Sun is the main source of visible light and of ultraviolet radiation (UV). There is enough evidence to provide support to the fact that childhood is a period particularly vulnerable to the exposition to UV radiation. On normal circumstances, kids absorb three times more UV radiation than adults and most of the exposition to sunlight occurs before the eighteen years of age. It explains why the fifty percent of UV radiation accumulated by an individual belongs to the childhood period.
Ultraviolet radiation and skin
Sun issues energy spontaneously in a way of electromagnetic waves. The light energy which reaches the surface of the earth is constituted in a fifty six percent of infrared rays (800 to 5000 nm), thirty nine percent is composed of visible light (400 to 760 nm) and five percent of UV radiation (290 and 400 nm). Infrared and visible radiations are innocuous for health; on the contrary the UV range is the cause for most of adverse reactions produced by sun.
UV radiation is subdivided in B type (UVB, from 290 to 320 nm) which is the most deleterious for health, and in A type (UVA, from 320 to 400 nm) which can potentiate the cutaneous effects caused by UVB light. Although UVA radiation is approximately one thousand times weaker than the UVB radiation, it enters on the surface on concentrations that are one hundred bigger than the concentration of UVB rays.
An important factor to consider is the fact that UV radiation also reaches body surface by reflection from snow (85%), sand (17%), water (5% and even 100% if sun is lighting perpendicularly).