Explain why can prolonged exposure to the sun damage our skin?

The mechanisms of sun exposure on the skin

When we expose ourselves to the sun, our skin interacts with an intense source of solar radiation. This interaction is primarily due to ultraviolet rays (UV). UV rays penetrate the outer layers of the skin and trigger various chemical and biological reactions. Our skin, on the front line of these attacks, first responds by producing more melanin, the pigment that gives off that lovely tanned hue. But this isn't just for appearance: melanin acts as a shield that absorbs some of the UV rays to limit damage.

When UV rays strike, they cause changes in skin cells. These rays stimulate the production of free radicals, those small unstable molecules that can wreak havoc in our cells. These free radicals damage lipids, proteins, and cellular DNA. Additionally, under the effect of UV rays, collagen and elastin, which are essential for the firmness and elasticity of the skin, degrade. The result: wrinkles, skin sagging, and other such delights. In short, sun exposure is a bit like sending your skin into battle without armor. It defends itself as best it can, but it always ends up taking the hits.

The role of ultraviolet rays (UVA and UVB)

Ultraviolet (UV) rays from the sun are primarily divided into two categories: UVA and UVB. UVA rays make up the majority of UV rays that reach the Earth's surface. They penetrate deeply into the skin, reaching the dermis. They are largely responsible for premature skin aging, wrinkles, and certain types of cellular damage. Although less numerous, UVB rays are more energetic. They mostly affect the epidermis, the outer layer of the skin. It is primarily UVB rays that cause sunburn. Both types of rays can damage the DNA in skin cells, which can lead to mutations and increase the risk of skin cancer. There is no immediate sensation of this change in the DNA, but the cumulative effects appear over the years. As for melanin, this natural pigment in our skin, it reacts to UV as a natural defense. However, even though it absorbs some of the rays, it cannot block them all. This is why unprotected exposure is risky.

Cellular damage and DNA

When we talk about sun exposure, we often think about tanning, but there are also less pleasant things happening beneath our skin. Ultraviolet rays, those invisible little critters, can cause serious damage to our DNA. Think of them as intruders attacking cells directly. They cause mutations, which are small errors in the genetic code. Normally, our cells have a repair system, but if the damage is too significant or too frequent, they get overwhelmed. The consequence: the risk of developing abnormal cells increases. And if it gets worse, it can lead to serious illnesses like skin cancer. In short, our skin is not very fond of UV rays, and it lets us know.

Premature aging of the skin

The sun is great for tanning, but it comes with its own set of problems for the skin. UV rays penetrate the skin and wreak havoc on collagen and elastin fibers, the proteins that give the skin its elasticity and firmness. When these fibers are damaged, the skin loses its structure and starts to sag and wrinkle. This is where premature aging comes into play. The brown spots that appear on the skin are also a visible sign of this wear and tear. We refer to this as photoaging, and it's not just a fancy scientific term. The skin can quickly become dry, rough, and wrinkles can set in much earlier than we'd like. Anti-wrinkle creams are often powerless against this deep damage. So, it's not just an aesthetic issue; this damage can also affect the protective function of the skin. That's why we take sunscreen seriously!

The risks of skin cancer

The ultraviolet rays from the sun, particularly UVB and UVA, are responsible for the majority of skin cancer cases. Prolonged and repeated exposure to these rays can damage the DNA of skin cells. When DNA is altered, it can lead to genetic mutations. These mutations can cause cells to proliferate uncontrollably, leading to the development of cancers. There are several types of skin cancer, but the most common are basal cell carcinoma, squamous cell carcinoma, and melanoma. Melanoma is the most dangerous because it tends to spread to other parts of the body if not detected and treated early. The risks increase with the intensity and duration of sun exposure, especially if the skin is not protected. Frequent sunburns, particularly during childhood, significantly increase the risk of melanoma later in life. People with fair skin, who burn easily, are particularly vulnerable. Sun protection, such as using sunscreen, wearing protective clothing, and seeking shade, can help reduce these risks.