The Sun, like any star, emits vast quantities of energy across a range of wavelengths. The light that's visible to us is only a small fraction of this energy. The human eye can only perceive electromagnetic radiation with wavelengths between 400 and 700 nanometres (nm), which is called visible light. Violet light, at 400 nm wavelength, and red light, at 700 nm, are the upper and lower boundaries of our ability to see radiation.

The smaller the wavelength, the higher the frequency, resulting in greater power and damage. Long-wavelength, low-frequency emissions that are beyond the visible spectrum, such as radio waves, are felt to be harmless, although longer wavelengths generally have greater penetrating power (for instance, radio waves pass through things light can't pass through). This is the same as with sound waves: you can hear the low, rumbling and thumping parts of the sound from your neighbour's stereo, and not the high notes, but it's the high, shrill notes that can hurt your ears.

Much of the energy emitted by the Sun is shorter-wave, more powerful radiation, most of it in the form of ultraviolet (UV) light. UV light's place on the electromagnetic spectrum is immediately above the most energetic form of visible light, which is violet.

UV is classified into 3 degrees of energy: UVA, UVB, and UVC. UVC has the shortest wavelength and the most energy, but it doesn't reach the Earth's surface because it's stopped by ozone in the Earth's atmosphere. UVA has the longest wavelength, the least energy, and the most penetrating power of the 3 types. UVB light is between the UVA and UVC in wavelength and energy.

Of all the UV light that reaches the Earth, about 95% of it is UVA. Because it has the least energy, it's less likely to burn skin than UVB, but because there's so much UVA, it plays a part in most sunburns.

Just as UVA penetrates the atmosphere better than more potent UVB and UVC, it also penetrates deeper into the skin. On a microscopic scale, UVA light is more likely than UVB to penetrate the upper skin layers and be absorbed by the basal skin layer. Although it's 1,000 times less potent than UVB, UVA exposure is believed by many experts to be more relevant to wrinkling and aging of the skin, and possibly to skin cancer.

When UV radiation strikes the body, the skin cells react immediately. Specialized cells produce melanin, the body's defence against UV radiation. People with naturally dark skin have more melanin and more melanin-producing cells. When light-skinned people are damaged by UV radiation, these cells produce more of this dark substance, creating a tan. Since they have fewer pigment-producing cells, the total amount of pigment (melanin) is low and thus the protection against further UV light is poor. So further exposure leads to sunburn and sun damage even if there is some tanning.

With higher levels of exposure, there's also an inflammatory reaction. Histamine, the chemical involved in most allergic reactions, is released in the skin, along with other inflammatory substances. Blood flow is increased and the skin turns red and warm to the touch. This occurs during sun exposure, but rapidly fades. It then comes back 2 to 6 hours later, with pain, as a sunburn. Typically, it's at its worst about 12 to 24 hours after sun exposure, but can peak up to 3 days after, and the soreness lasts about 3 days. After 4 to 7 days, the outer layers of skin peel off and the redness fades.

Any sunburn is a real burn caused by real heat, delivered over time in tiny packets too small to notice. With extremely high doses, sunburn can result in second-degree burns, with severe blistering of the skin, dehydration, fever, and nausea.

Actinic keratosis (AK) is a rough, scaly skin lesion that appears on sun-exposed areas of the skin. AKs are caused by exposure to UV light. They are not cancerous, but may lead to skin cancer if not treated. AKs are usually pink and scaly.

People experiencing sunburn often have skin that is red, swollen, or sore to touch. Have a doctor or health care professional look at the sunburn if you notice a rash, itching, or fever, or if blisters appear. Darker skin tones may not appear red; however, people with dark skin can still get a sunburn.

There's no quick fix for sunburn. Like any burn, it takes time to heal. Acetaminophen*, nonsteroidal anti-inflammatory drugs (NSAIDs), cold water compresses, and cool baths can help with symptoms. Skin hydrating and moisturizing creams may also temporarily relieve pain. Many people believe these can also reduce eventual peeling, but this isn't proven.

Butter, an old sunburn remedy, is inappropriate, as it increases the risk of infection. Soap should be kept clear of burned areas as it's an irritant. Anaesthetic sprays or creams should also be avoided unless recommended by a doctor.

In extreme cases, with blistering and large areas of second-degree burns, the sunburn victim is admitted to a burn unit at the hospital. Treatment is identical to that received by other burn patients, including steroids and fluid replacement.

The best advice for sunburn is to avoid it completely. The recommendations given by public health experts on sun exposure generally consist of this:

• Avoid the sun completely between 11 am and 4 pm, when the sun's rays are most intense (you know the sun's rays are most intense when your shadow is shorter than you are).
• Wear sunblock with sun protection factor (SPF) of 30 or higher, preferably one that protects against both UVA and UVB, whenever you are outdoors. Reapply at least every 2 hours, and more often if you are swimming or sweating.
• Don't rely just on sunblock – tightly woven clothes and hats provide even better protection.
• Don’t be fooled by cloudy days – up to 80% of the sun’s radiation reaches the earth even when it’s cloudy. Always protect exposed skin.
• Don't just worry about the sun in summer – UV exposure is a year-round problem. Snow reflects 80% of UV light, compared to only 20% by sand – that's why skiers get sunburn. 

If you notice any skin changes, including new growths or moles, see your doctor.

In spite of what is known about the risks of sunburn, many Canadians still prefer the look of a "healthy" tan. As an alternative, many self-tanning products are available today that produce the appearance of a tan without the damaging effects of UV rays.

All material copyright MediResource Inc. 1996 – 2020. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source: www.medbroadcast.com/condition/getcondition/Sunburn