What effect does sun have on our skin?

Benefits of Sunlight

Sunlight is overall a wonderful joy that provides warmth, light, and health for us not only in our lives but also so that we can live and get through the day. Sunlight is the most effective way at getting vitamin D- humans can actually get enough vitamin D synthesized in the skin from sunlight that they do not need to consume any in their diet.  Adequate vitamin D levels are necessary for health, but can also help reduce acne, improve elasticity, and lessen aging effects in the skin. However, as we all know, spending too much time in the sun over the long run can actually be quite detrimental to skin, putting people at risk for sunburns and skin cancer. Prolonged exposure to the sun has also been linked to aging skin including findings such as brown spots, sallowness, drying, and increased wrinkles, so it is important for everyone to have a healthy, yet not damaging amount of sun exposure.

Composition of sunlight

Sunlight is composed of two main types of ultraviolet light, divided by the wavelength. Both can be beneficial in some ways, and harmful in others, and can overall effect skin in very different ways. Ultraviolet A light is basically constant throughout the day. This is the type of light mostly responsible for immediate tans when someone is out in the sun all day long. It is also the main type of light used in sunless tanning.  UVA light is the less damaging of the two, but affects the deeper layer of the skin, or the dermis, which is the more permanent of the two. Thus it is also most responsible for aging of the skin. UV light can damage elastin fibers in the skin by a process known as elastosis, which can cause the skin to sag and stretch over time, leading to wrinkles and dry skin. Normally your skin has enzymes called metalloproteinases which fix damage done by sunlight, but when this damage is done daily and for years, it can still cause long-term problems that cannot be fixed by enzymes. Ultraviolet B is slightly different. UVB light varies in exposure throughout the course of the day. It is most notable from about 10am to 5pm. This is the light that is mostly responsible for sunburns, and tends to be obvious about 6-12 hours after exposure. UVB light tends to affect the top layer of skin or the epidermis. It is typically the type of light noted to be most responsible for skin aging and skin cancer, and thus tends to have more press as “bad light”.

UV light in general is also thought to increase amounts of free radicals in the skin, which can damage cellular function, as well as cause more wrinkles and long-term damage. Again, the body has defenses to help fix some free radical damage, the problems start to occur with long-term exposure. Free radicals and UV light can also cause damage to cellular DNA and RNA, part of the reason why long-term exposure increases the risk of skin cancer .

How to avoid skin damage from the sun

Sunscreen is very important for good skin care when out in the sun, for both fair and dark-skinned complexions. Sunscreens provide protection against both UVA and UVB light. Sunscreen with SPF 15 should be applied at least 20 minutes before going outside for optimal skin care. It's important to re-apply every two hours, and to try to avoid staying outside often from 10-4pm due to high levels of UVB light. It's also important to remember that cloudy days do not totally protect from ultraviolet light, so care must be taken to either cover skin with clothing or sunscreen on cloudy days as well.