This year, over a million new cases of skin cancer will be diagnosed in the United States alone. Although, skin cancer is unlikely in children, the cumulative effects of sun exposure that occur during childhood, contribute dramatically to the rising incidence of skin cancer in adults.
What causes sunburn?
The sun produces a number of waveforms including sound waves, microwaves, visible light waves, and ultraviolet (UV) light. UV light is responsible for the sun related effects we shall be discussing and is composed of several different forms, classified by wavelength. The UV waves that injure the skin are UVA1 (340-400nm), UVA2 (320-340nm), and UVB (290-320nm). UVA waves are primarily responsible for aging (A is for aging) and UVB waves are primarily responsible for sunburns (B is for burns). UVB waves have the ability to cause more skin damage, but they reach the earth in much smaller quantities than UVA. The primary contributors to sunburn are UVB and UVA2. Sunscreens only have to block some of the UVA2 rays for the manufacturer to claim UVA protection. Remember also, that UVB waves do not penetrate glass but UVA waves do. You really can get a sunburn from sitting inside a car or sitting next to a window!
A sunburn is usually classified as a first-degree burn. It involves an immediate reddening of the skin, followed by a more intense delayed reaction that is accompanied by leakage of blood vessels and can lead to blistering. The top layers of skin are actually destroyed; hence, the peeling seen within 3-7 days.
How are different skin types affected?
Individuals with Type I skin always burn easily, never tan and are extremely sun sensitive. Type II individuals usually burn easily, tan minimally and are very sun sensitive. Type III individuals sometimes burn, tan gradually to light brown and are moderately sun sensitive. Type IV individuals burns minimally, always tan to moderate brown and are minimally sun sensitive. Type V individuals rarely burn, tan well. Finally Type VI individuals never burn. Clearly, people with Types I-III are at greater risk for skin cancer but skin cancer can also occur in deeply pigmented people of African American heritage.
Tanning is a 2-stage process, and unfortunately a tan also represents damage to the skin. The UVA causes chemical changes in existing melanin, which darkens and produces the immediate color change. Within 48 hours, new melanocytes (melanin/pigment producing cells) are formed, primarily by the UVB, for more lasting color. Obviously the degree of this reaction is different among different skin types.
So what’s wrong with sun exposure?
Over the years, UV light (A&B) damages the elastin fibers in the skin that are responsible for the soft, firm texture of human skin. As a result, with more prolonged exposure, one begins to notice wrinkling, sagging and a generally weather-beaten appearance to the skin (this process is known as photo aging). But if this were the only side effect of prolonged sun exposure, most healthcare providers would not complain. What is more concerning is that chronic sun exposure weakens your skin’s immune system and increases the likelihood of cancerous changes in the skin.
There are 3 types of skin cancer. Basal cell carcinoma is the most common form of skin cancer, is seen in the 30s and beyond, and is clearly related to fair skin and sunburning. There are many clinical forms of this disease; however, if treated early and effectively, a cure can be achieved. Recurrences are common. Squamous cell carcinoma is a more serious disease. It is usually seen in the 50s and 60s and also appears in sun-exposed areas like the scalp and ear. If treated early, this disease generally has a good outcome. The most serious problem is malignant melanoma. This form of cancer is one of the most dangerous, with early spread to the entire body. It usually shows up as sudden, irregular darkening of a previous mole or birthmark. Crusting, bleeding and increased growth are all concerning characteristics. This disease can occur at any age, although it too, is more common in the 30s and 40s. The single most important risk factor for malignant melanoma is sunburn-especially severe sunburn as a child.
One in 7 Americans will develop skin cancer at some point in their lifetime and most cases are directly related to sun overexposure. Skin cancer is not seen immediately. Most of the time there is a time delay of 40-50 years, demonstrating that the actual damage occurred at a young age. It is estimated that 80% of one’s lifetime sun exposure occurs under age 20, and this strongly determines the chances of developing skin cancer later in life. In fact, 2 severe burns in childhood show a significant increase in risk for skin cancer, and accumulating 5 such burns doubles the risk. Unfortunately, most people don’t become conscious of skin protection products until they are in their 20s and by that time it may be too late.
What sunscreen should be used?
There are two basic types. Chemical sunscreens (PABA, cinnamates, benzophenones and salicylates) work by selectively absorbing UV light and acting like melanin. As previously mentioned, a sunscreen only needs to block part of the UVA2 rays to claim UVA protection, most sunscreen chemicals cover the UVB rays and only the shorter UVA waves. Physical sun blocks (zinc oxide and titanium dioxide) work by scattering UV rays and offer complete protection from UVA and UVB.
PABA is para-aminobenzoic acid, a chemical responsible for certain allergic skin reactions. Many sunscreen products have abandoned PABA, but may contain a PABA derivative. The ingredients with the broadest spectrum sunscreen coverage are: oxybenzone, dioxybenzone, and menthyl anthranilate. The only chemical that covers the entire UVA spectrum is avobenzone (Parsol 1789); it needs to be applied frequently and is not widely available. Most sunscreens are a combination of several chemicals in order to provide a good range of protection.
The SPF provides an indication of how long you can stay in the sun after applying a sunscreen before burning. For example, if you normally start to turn pink after 10 minutes in the sun without protection, a sunscreen with a SPF of 15 would allow you to stay in the sun for 150 minutes before getting the same burn. To be sure, skin character is a major determinant in the choice of your SPF. Light skinned (even if associated with dark hair) people burn more readily than dark skinned individuals. The sun’s intensity is increased by many factors, indicating a need for more protection: location (closer to the equator), altitude (the higher the altitude, the more UV-B), time of day (the sun is strongest from 10 AM - 3 PM), genetics (people with a family history of skin cancer or dysplasia are at a higher risk) and reflection (the sun reflects better off of sand, stone, and water-and can actually bounce up under your beach umbrella!).
SPF ratings are done in a laboratory and apply only to UVB protection. Scientists are unable to calculate the degree of UVA protection, although it is present. An SPF 15 offers 93% protection from UVB rays; SPF 30 is 97% protective. Interestingly, SPF 64 is only 98.4% protective, demonstrating the diminishing returns of investing in an SPF>30. This protection rating only applies if the sunscreens are used properly! (See below)
So how high of SPF is enough?
It is recommended to always use at least an SPF 15, but as discussed above there is little evidence to support spending your money on anything over 30, except possibly for children under a year.
How much sunscreen is enough and how often should it be applied?
Unfortunately, studies show that most people use too little sunscreen. The average adult requires 1 ounce of sunscreen to cover a swim-suited body. One ounce is quite a bit. If you use half as much, you get half the protection. It doesn’t matter if it’s a spray, gel, cream or mousse or whether it is purple or clear; you still need 1 ounce for proper protection. You should use up several bottles of sunscreen on vacation!!
The frequency of applying sunscreen depends on how much you sweat and how often you wipe yourself with a towel. Waterproof sunscreen doesn’t wash off as easily, although it does eventually. It certainly still wipes off, and also needs to be replaced periodically. Recommendations are to reapply every 2 hours, sooner for a lot of swimming and towel use. Zinc and titanium can be messy, but bad burns can be prevented with these products if the sun is unavoidable. Also consider them for lips, ears, and noses.
Dermatologists recommend application 30 minutes before actual sun exposure so that it has a chance of being absorbed in the skin. The scalp, nose, ears, lips, and tops of feet are often the most neglected areas so you need to be generous with your sunscreen!
What about sunscreen for infants? The American Academy of Pediatrics does not recommend applying sunscreen on children under 6 months old but rather keeping them entirely out of direct sun with the use of hats and umbrellas. If direct sun is unavoidable, apply sunscreen only to the backs of their hands and to their faces. Look for zinc oxide as the only active ingredient in baby sunscreens if possible.
Can you use last year’s sunscreen?
The American Academy of Dermatology says that even without an expiration date, most sunblocks can be used safely for at least 3 years.
Overall, being out in the sun is healthy for you. It increases vitamin D conversion; it helps clear up sensitive skin and imparts a feeling of well-being. But it should be used in moderation. Children should wear sunscreen, hat and sunglasses. Sunglasses labeled 99-100% UV protection will help prevent cataracts later in life! Buy an inexpensive, waterproof, SPF 30 product. Try to avoid exposure between 11 AM and 3 PM and wear protective clothing if possible. And try to teach your children at an early age that taking along the sunscreen is just as important as the towel and the beach ball.