UV Radiation and Your Skin
The skin protects you against the intrusion of harmful substances, organism and radiation.
The outer layer, epidermis, takes most punishment. It is insensitive and contains no blood vessels. Unfortunately it is also very thin, so pain and damage easily reach the lower layer – the dermis. Nerve fibre, blood vessels, hair roots, sweat glands, DNA and collagen fibres, to name a few, are located in this layer. If your skin is unprotected, UV radiation penetrates deep into the dermis.
Your skin is able to defend against mild radiation attacks. Skin cells produce melanin, the substance that tans your skin. Suntan is a weak shield against the harmful radiation – some skin cells die during the battle and form a protective horny layer of dead tissue. The skin repairs most damage to the cells and discards the victims. In your lifetime you shed approximately 18kg of skin.
Frequent exposure or high doses of UV radiation may lead to temporary or permanent changes to your skin, passing sunburn being a painful indicator. Too much damage will show up in wrinkles and dry skin. These are the signs of damage to the collagen fibres. The skin ages prematurely and permanently – photoageing. A billion-dollar cosmetic industry tries to sell products that promise to prevent, minimize or repair the damage, or at least hide it.
DNA is the ‘repair manual’ of the skin. UV radiation is capable of seriously distorting the information contained in the DNA instruction book, however, and the repair process may not proceed on its intended path and could instead lead to skin cancer. Skin cancer occurs mostly in fair-skinned people, but it is uncertain whether prolonged exposure, high doses or exposure at childhood increases the risk.
Loose, dry, rough and leathery skin; deep wrinkles and furrows; skin that is unevenly pigmented and covered in brown freckles or other blemishes; if that’s what your skin will look like at old age, you have done well. Many others reach this weather-beaten look at the age of 30 or 40. Photoaged skin is the term for the signs and symptoms and photoaging describes the process.
Too much sunshine changes the structure of the skin permanently and is responsible for premature skin blemishes such as:
- Wrinkles. UV radiation damages collagen fibres. The repair process becomes rather disorganized and collagen fibres form where they shouldn’t, resulting in wrinkles.
- Solar elastosis. Damage to collagen triggers additional production of elastin. Excess elastin stretches the skin and forces it to sag and form furrows. The skin of the neck and the upper back are usually the least protected and suffer most.
- Stellate or sun scars. Excessive exposure to the sun takes its toll on sweat and oil glands. They are no longer able to function efficiently, thus depriving the skin of moisture. The skin becomes dry, thick, scaly and scars easily. Wounds tend to heal slowly.
- Solar or senile purpura. The fine blood vessels in overexposed skin rupture quite easily, resulting in slow-healing bruises, especially on the hands and forearms. The bruises can look alarming but are generally harmless.
- Freckles (also named liver or age spots) can occur at any age. They are most common on the fair skins of children and of adults over the age of 55, particularly on the sun-exposed skin such as hands, face, arms and shoulders. These flat brown or black spots can be tiny or several centimetres in diameter. Cosmetics can either hide the blemishes or bleach the colour.
- Solar comedones. A little more annoying than freckles are solar comedones, pimples that look like acne but are not related. The blemish is also known as Favre-Racouchet disease. The pimples occur predominately on the face and are either open (blackheads) or closed (whiteheads). Comedones develop after considerable exposure to UV radiation and appear more often on the skin of heavy smokers.
Of course, this process doesn’t happen overnight. The effects accumulate over the years and the result depends very much on the frequency and intensity of exposure to UV radiation. While heat, wind, and air pollutants also accelerate photoageing, UV radiation is to blame for about 90% of the symptoms.
It is spring at last: you get out your shorts or swimsuit and are determined to enjoy the first warm and sunny days. Curiously, after just a short while and despite sunscreen, your skin starts to itch and turns red in patches. Some tiny blisters or pimples also spring up. No wonder, you kept your skin covered for a long time over winter and your skin has become light sensitive. In this scenario, the symptoms are probably only temporary and will disappear once your skin gets used to the UV radiation.
Others are not so fortunate. Even low levels of light, as during wintertime, can trigger minor or major reactions. These people suffer from photosensitivity. As with allergies, a variety of substances or disorders can trigger the symptoms. It can be something such as food or medication, or it can be a skin-care product. Certain medical conditions trigger photosensitivity or UV radiation can aggravate the condition.
The number of cases with mild to moderate photosensitivity is not easily established. Minor symptoms are often mistaken for a typical reaction to UV radiation, such as sunburn. This can be very tricky when a sunburnt person tries to counter the effects and applies sunscreen that contains sensitivity-increasing chemicals.
Disorders resulting from Photosensitivity
Polymorphic light eruption is a fancy name for rashes. It is the most common disorder associated with photosensitivity and affects an estimated 10% of US citizens and around 20% of Swedes. The real number is probably higher as most minor occurrences aren’t reported. The disorder appears in all races, but more frequently in fair-skinned women.
Burning or itching rashes, consisting of red spots, patches or blisters, show within 1 to 4 days of exposure to UV radiation, usually on arms and lower legs. If the person avoids further exposure, the symptoms disappear within a couple of weeks but can recur after another exposure. But because the skin adapts to sunlight, the effects should become less severe every time.
Chronic photosensitivity dermatitis, also known as chronic actinic dermatitis, is another result of photosensitivity. It is widespread, but this time affects elderly male more often than it does women. Inflamed and itchy patches appear on the exposed skin. Scales and pimples can accompany the eczema.
Sun hives (solar urticaria) is a rare skin condition. It usually doesn’t comprise more than 5% of all photosensitive skin disorders. People of all races, age and gender can contract this disease. Its symptoms are usually red swollen patches that intensely sting or itch.