Calvert Creak
Skin Care Information
How the Sun Damages the Skin
Excessive exposure of the skin to sunlight is the number one cause of skin damage. Most of us are aware of this and therefore take steps (such as wearing protective clothing and sunscreen) to protect ourselves from this damage.
Because the sun is such a major contributor to skin damage, it is useful to know exactly how and why the sun causes its damaging effects.
What is Sunlight?
The light that emanates from the sun contains several spectrums of radiation. These are:
- Ultra-violet (UV) radiation. This is the most relevant and most damaging of the spectrums of sunlight. There are actually wavelengths of UV:
- UV-A, once thought to be harmless because it doesn’t cause sunburn, is now known to cause a great deal of skin ageing and skin cancer. UV-A penetrates deeper into the skin than UV-B. The intensity of UV-A is constant, regardless of the time of day or the season of the year.
- UV-B is the wavelength that causes sunburn, skin ageing, wrinkles and several types of skin cancer. UV-B is most intense between the hours of 10:00 am and 2:00 pm. It is also most intense during the Summer months and least intense during Winter.
- UV-C has not been a cause of concern until recently. The earth’s ozone layer normally filters out this spectrum of UV, preventing it from damaging the skin. However with the recent phenomena of the hole in the ozone layer, more UV-C is reaching the earth (especially in the southern regions of Australia).
- Infrared radiation comprises approximately 60% of the rays of sunlight that reach the earth. The skin absorbs about 93% of infrared radiation that reaches it. Infrared radiation is thought to be harmless and is likely to actually confer some health benefits.
- Visible light is the spectrum of light that we actually “see”. This spectrum is beneficial to humans.
- X-rays and gamma-rays. These are highly dangerous forms of ionizing radiation that easily cause various types of cancers. Luckily these rays are prevented from reaching the surface of the earth (and the surface of our skin) by dust particles and moisture doplets in the atmosphere and the earth’s ozone layer.
Sunlight Causes Wrinkles
The main cosmetic reason that most people need to minimise their sunlight exposure is the fact that sunlight is a definite cause of wrinkled skin. In the dermal layer of the skin, sunlight’s UV-A and UV-B rays cause the skin’s most important structural protein, collagen, to break down at a higher rate. These UV rays also cause the accumulation of abnormal elastin (another important structural protein in the skin which is responisble for the skin’s elasticity. When UV-damaged elastin accumulates, large quantities of metalloproteinases (a group of enzymes including collagenase and elastase) are produced. These metalloproteinases malfunction and begin to break down the skin’s collagen into disorganised collagen fibers known as solar scars. With time, this imperferction in the skin’s rebuilding process directly causes wrinkles.
Researchers estimate that exposure to UV-A and UV-B from sunlight are responsible for 90% of wrinkles. Look at those areas of your skin that rarely or never receive sunlight exposure (your bottom for instance) and notice their totally wrinkle-free status.
Sunlight Generates Free Radicals
The UV component of sunlight generates large quantities of free radicals in the skin. Free radicals can be likened to microscopic atomic bombs going off in your skin, as they are unstoppable biochemical reactions. UV-A generates free radicals named singlet oxygen free radicals and UV-B generates peroxyl free radicals, both of which contribute to skin ageing and wrinkles. These free radicals also contribute to age-related macular degeneration (which eventually leads to blindness) in the eyes; and are powerful initiators of skin cancer.
Sunlight Damages DNA
DNA (deoxyribonucleic acid) is the genetic material present in every cell of your body. Sunlight’s UV-A wavelength damages (mutates) DNA in the skin which can lead to skin cancer and wrinkles. UV radiation also damages the body’s enzymes that normally repair damaged DNA.
Sunlight Impairs the Skin’s Immune Function
Although the body’s immune system is generally seen in terms of its white blood cells, the skin contains highly specialized immune cells called Langerhans cells. These “outposted” cells of the immune system help to suppress toxic microorganisms and also play a role in cancer prevention. Sunlight’s UV radiation severely damages Langerhans cells and also reduces the number of Langerhans cells present in the skin.
Sunlight Causes Cell Death
When the body’s cells become damaged, your body puts into place a process named apoptosis to deal with the damage. Apoptosis can be likened to cellular suicide, in that apoptosis kills off damaged cells so that they cannot further replicate. This is useful as further replication of damaged cells is the starting point for cancer. Sunlight’s UV content prevents this cellular suicide, permitting deformed cells to continue replicating which can lead to them becoming cancerous.
Sunlight Changes the Skin’s Texture
Sunlight’s UV wavelengths cause inappropriate thinning and thickening at various skin sites. For instance, exposure of the back of the neck to excessive UV results in very thick skin that appears as very coarse wrinkles. These wrinkles are so thick that they do not disappear when the skin is stretched. Outdoor workers’ and farmers’ necks are good examples of this type of inappropriate thickening of the skin.
UV exposure can also cause solar elastosis which appears as thickened coarse wrinkling and yellow discoloration of the skin.
On the face, UV can cause thinning of the skin which results in fine wrinkles, for example crow’s feet around the eyes.
Sunlight Damages the Skin’s Blood Vessels
Sunlight’s UV wavelengths can damage the walls of the skin’s blood vessels, which facilitates “easy” bruising. This damage can also cause spider veins (telangiectasias) which are tiny blood vessels visible to the outside world.
Sunlight Interferes with Skin Pigmentation
The most visible alteration in skin pigmentation that occurs after sunlight exposure is the appearance of freckles. Light-skinned persons experience the most noticeable freckles, which occur when melanocytes (cells which produce the skin’s pigment, melanin) are damaged by UV exposure. This damage causes the melanocyte to become larger and therefore more visible to the outside world.
UV exposure is also directly responsible for age spots (liver spots) on the hands, chest, arms and face.
When long-term UV exposure actually destroys melanocytes, visible white spots occur because of the lack of melanocytes that normally produce melanin in the skin.
Sunlight Causes Moles and other “Bumps”
Sunlight’s UV content increases the appearance of moles in regions of the skin exposed to sunlight. Via similar mechanisms, UV also causes precancerous bumps known as actinic keratoses, especially on the face, ears and on the back of the hands. These actinic keratoses are deemed to be precancerous as approximately 1% of them develop into a form of skin cancer named squamous cell carcinoma. Another type of keratoses, seborrheic keratoses is also caused by UV. These look a lot like warts (and are sometimes known as senile warts) and are quite unsightly.
Sunlight Causes Skin Cancer
Almost everybody is now aware that sun exposure can cause skin cancers. There are three principal types of skin cancer – basal cell carcinoma, squamous cell carcinoma and melanoma.
Basal cell carcinoma is caused by excessive exposure to UV-A. It is slow-growing and develops over a period of months or years. This type of skin cancer usually occurs on the face, ears, lips or mouth; and generally doesn’t spread to other parts of the body.
The symptoms of basal cell carcinoma are:
• An open sore that persists for three weeks or more.
• An irritated red or reddish-gray area that may be painful or itchy.
• A smooth, round growth (bump) with an elevated border.
• A pearly or translucent nodule that resembles a mole; this can be red, pink (most commonly), white, black, or brown.
• A white or yellow lesion that is similar to scar tissue.
Basal cell carcinomas are the most common type of skin cancer, accounting for 80% of all skin cancers.
Squamous cell carcinoma is caused by excessive exposure to UV-B and usually appears on the face ears, lips, nose or the backs of the hands. It is more aggressive (can spread to other parts of the body) than basal cell carcinoma and can be deadly if ignored for too long. The symptoms of squamous cell carcinoma are:
• Wart-like bumps that are flesh-coloured or reddish.
• A thick-scale on a skin-colored pimple or lump. They often look like a red scaly patch.
• Squamous cell carcinomas are had to the touch – as they enlarge they may ulcerate or bleed.
Squamous cell carcinoma is the second most frequently occurring type of skin cancer.
Melanoma is the most deadly type of skin cancer – it is lethal in approximately 20% of cases. UV-B exposure is thought to be the cause of melanoma. The more incidents of sunburn that an individual suffers during childhood, the greater the risk of future melanoma.
Melanomas look like spilled ink and differ from moles in that they do not have even borders like normal moles.
