The sun showers us with a mystifying palette of radiation; that part which causes sunburn and related problems is a form of ultraviolet radiation called UVB. The amount of UVB that strikes our skin directly determines how much damage we sustain. There is a more damaging form of ultraviolet light called UVC, but fortunately it is completely blocked by atmospheric ozone. Should ozone somehow disappear, the effect on all living creatures would be devastating, hence the concern about the ozone depleting effects of certain types of aircraft, aerosol propellants, and refrigerants.
Many factors determine how much UVB strikes us at any given time. Exposure is maximal when the sun is at its highest point; thus we receive more at noon on the summer solstice (late June) in the lower latitudes. Atmospheric conditions likewise effect exposure: smoke absorbs and thus blocks UVB quite well. Conversely, dust and water scatter UVB, “bending” the rays, which increases our exposure. This accounts for severe burns received by individuals who mistakenly believe they are in no danger of sunburn on a dull, hazy, or even cloudy day. Light colored sand reflects substantial UVB, and water at high noon can reflect as much as 100%, causing the unsuspecting person sitting under a beach umbrella to sustain sunburn.
One function of our skin is to protect us from the effects of UVB. Skin produces urocanic acid, an oily substance which absorbs UVB, sort of a natural sunscreen. The cells of the top layer of skin, or epidermis, reflect, scatter and absorb UVB. They are thus damaged and sloughed or peeled off, then replaced. UVB which penetrates to the deep layer of the skin (dermis) causes cumulative and irreversible damage which plays a role in the genesis of squamous and basal cell cancers, as well as aging and wrinkling of the skin.
The substance in our skin which gives it pigmentation or “color” is melanin. Melanin provides somewhat of a protective effect against UVB. The amount of melanin found in skin varies widely with race and sun exposure. Melanin is what makes Caucasians “tan,” and many people spend thousands of hours in damaging sunlight or tanning beds trying to achieve a healthy, sexy appearance.
Sunburn and Tanning
When a person is exposed to bright sunlight at mid day for several hours without any form of skin protection, redness, itching, and then pain occur within a few hours. The redness is caused by dilation of the tiny blood vessels in the skin, which also accounts for the palpable warmth. Secondary heat loss can be significant, resulting in “chills.” The effects peak in 12-24 hours, and at this point the skin is much more vulnerable to further acute burn. Dark discoloration and blisters may form. Wind increases the burning effect of UVB, as does heat, humidity, and water immersion.
Following exposure, our skin mounts several defensive mechanisms. First, the existing melanin is converted to a darker form that is more effective at absorbing and blocking UVB. Later, production of melanin is increased, providing more protection and creating a “tan.” This takes several days to occur, and varies among individuals. Even a dark tan allows some UVB to reach the deep skin, and ongoing damage will continue to occur. Lastly, the epidermal layer thickens, providing somewhat of a protective yet unsightly effect.
Protection from UVB
Clothing is an excellent barrier to UVB; an exception is wet white cotton which provides minimal protection. A wide brimmed hat gives good but not complete protection to ears, noses, and the top of the scalp. Remember, reflected light from the water or beach can find its way under a hat and cause substantial damage. Long sleeved shirts of lightweight material are also very effective.
Sunscreens are widely used and even more widely misunderstood. There are two types: those that reflect UVB and those that absorb it. The most common reflective agent is zinc oxide. Now available in an array of gaudy colors, zinc, when applied thickly and maintained over time, provides almost 100% protection. It is useful when applied to previously burned areas, it is problematic in that it gets on clothes and towels, and is relatively easy to accidentally wipe off. Many people won’t use it due to its appearance, or won’t make the effort to reapply, thus limiting its effectiveness.
Most absorptive sunscreens contain para-amino benzoic acid (PABA) or one of its derivatives (including benzones) or cinnamates, mixed with various oils and scents. PABA-like compounds penetrates the top layer of the epidermis and binds to it, where it absorbs UVB and blocks it from penetrating further into skin. Repeated applications result in an accumulation in the skin, thus enhancing its effectiveness. The term “SPF” (sun protection factor) gives a rough estimate of the amount of sun blocking agents found in a given product, and its relative efficacy in terms of protecting the user from sunburn.
Unfortunately, PABA, its derivatives, and many additives are easily rinsed from the skin by perspiration and swimming. Some products use heavy oils in an attempt to augment longevity in a wet environment, but many users find this degree oiliness “greasy” and won’t use them. Some of the worst sunburns have occurred in people who used a product with a high SPF on the way to the beach and mistakenly believed they were protected for the rest of the day.
What’s the Answer?
You live in North Dakota, your skin hasn’t seen the light of day in months, and you’re planning a two-week vacation to a tropical destination such as Abaco. The latitude will be substantially lower, the sun higher, you want to be out in the sun every day, and if you’re not careful, you’ll sustain a sunburn on Day 1 severe enough to ruin your vacation, or at least keep you indoors for several days. What to do?
We mentioned repeated applications of sunscreen resulted in its accumulation in the skin. Penetration of PABA (as well as many other topical agents) is enhanced if applied on thoroughly dried skin after a warm shower. Therefore, we recommend you purchase a large container of whatever sunscreen you like with an SPF of at least 15 and apply it daily as noted above for at least a week before you leave for your vacation! Cover every inch of skin you plan to expose. Be particularly mindful of your nose, ears, chest, hands, and the tops of your feet. Continue this when you reach your destination. After application, do not let your skin get wet for at least two hours, as this will result in rinsing of the agent. Take a wide brimmed hat, at least one long sleeved shirt, a large container of SPF 15 for repeat applications, and a tube of zinc with you.
If you can’t work this into your routine, the next best tactic is to put on your sunblock before you leave your room in the morning, either after showering or as part of your departure routine. Be especially mindful of your children: their skin is more fragile, they’re in and out of the water more often, and they are less tolerant of the pain associated with a bad burn. Repeat applications frequently, and try to keep them dry for a while thereafter. If you are in a boat, keep the Bimini top up. Make sure everyone in your party has good sunglasses; polarized lenses are not as trendy as the metal coated “bug eyes” that have become popular, but they offer much better protection as well as enhancing your ability to see into the water.
Recently a number of innovative, albeit expensive, sun protection products have appeared on the market. Many of these are being distributed by dermatologists. I know of one that is an “invisible “ zinc oxide formulation. A three-ounce tube sells for $45! Zinc, as has been previously discussed, is a very effective sun block, and it may be worth the considerable expense to have such a product that is cosmetically acceptable. Consult your local dermatologist for such products.
Many people have ignored this advice: “I want to get a tan, how can I tan with all this sunblock?” Believe me, it will happen! The object is to do it gradually, not all on your first day. If you are careful you will have a great tan and will have avoided suffering from sun exposure. Why go to all this trouble?
Treatment for Sunburn
The short answer is, there really isn’t any effective treatment. There are topical agents that contain aloe and local anesthetics which may decrease the local discomfort, and it’s worth taking a container with you on your trip. But the hard truth is, nothing can undo the burn once it occurs. If you’re on vacation, you will be tempted to ignore your sunburn and go back out the next day, whereby your skin’s increased vulnerability will cause it to burn even more severely. And don’t be fooled into thinking you won’t get burned on a cloudy day. UVB penetrates cloud cover nicely, and that scattered radiation will get under your hat and umbrella and fry you! Please be careful, you’ve put so much time and money into your vacation. Don’t ruin it by being careless with your skin. Take a little time before and during your trip to prepare for the sun; it’s an effort that will really pay off.