Without the Sun, life on Earth would have no hope. A star that warmed our little rocky planet helped create the conditions that made life possible in this little corner of the cosmos. Yet, somehow, some people seem to have developed allergies to sunlight.
Sunlight is made up of a spectrum of radiations electromagnetic that includes visible light, infrared (heat) and ultraviolet (UV), the latter being responsible for sun damage that ranges from irritating to painful and deadly.
Dr Robert Sarkany, head of photodermatology at St John’s Institute of Dermatology, Guy’s and St Thomas’ Hospital: “If you break up sunlight with a prism, you will find that you have a range of colors in the rainbow, but only the visible ones, from the shortest to the longest wavelengths. However, if you put your hand in it, you won’t see anything, but it will feel hot: that’s infrared. You can’t see or feel anything, but if you stick your hand in there long enough, you’ll get burned. These are ultraviolet (UV) and represent 5% of what the Sun sends us.”
Sun allergy
UV light can penetrate the skin because it happens that the energy from a photon UV it matches the energy gap between electron orbitals in the type of carbon-containing molecules that make us up: proteins, DNA, and lipids.
“So this is a very physical way of saying that UV chemically changes the biochemicals that make up our pathways and so any parts of the body that are exposed to daylight will change. It will go through the first millimeter or two of skin and what you’re going to have is the very worrying situation that all the time the cells are exposed, their DNA is being changed and you’re going to have mutations and changes in the DNA,” keep going Dr. Sarkany.
What are the body’s defenses against radiation? solar and UV? In essence, daylight is a uniquely ubiquitous, potentially very dangerous thing that clearly harms everything it encounters in the body. As a result, we have had to develop a very, very sophisticated immune system to deal with this major threat that can cause cancer, autoimmune diseases, induce DNA mutations, etc.
So how do we deal with this? We have three major answers: producing pigment in the skin so that less damage occurs tomorrow. You tan fast enough to protect yourself from UV exposure, so if the same thing happens tomorrow, they will be absorbed and not reach your DNA.
There is also an intracellular, complex DNA repair pathway to seek out all those bits of DNA damage and remove them before they turn into mutations like cancer. Cells whose DNA is irreparably damaged are thrown into cell suicide, also known as apoptosis. They die and that causes the reaction we see as sunburn.
