Patient education: Sunburn prevention (Beyond the Basics)

OVERVIEW — Sunburn is the inflammation of the skin resulting from exposure to the sun's ultraviolet (UV) rays, especially ultraviolet B (UVB) rays. Typically, sunburn is maximal about 24 hours after exposure. There are several effective ways to prevent sunburn, including staying out of the sun during peak hours, applying sunscreen, seeking shade, and wearing protective clothing. While these measures are important for everyone, they are especially important for children and people with lightly pigmented skin, who burn easily and tan poorly.

This article discusses ways to prevent sunburn. The treatment of sunburn is discussed separately (see "Patient education: Sunburn (Beyond the Basics)"). More detailed information about sunburn is available by subscription. (See "Sunburn".)

AVOID SUN EXPOSURE — It is important to prepare for sun exposure, especially if you plan to be out in the sun for an extended period of time or during the middle of the day, when the sun is at its highest and its ultraviolet B (UVB) rays are strongest (10 AM to 4 PM during daylight savings time in the continental United States). Particular care must be taken at high altitude (eg, mountains) because UVB intensity is greater.

Even on cloudy days, it is important to protect your skin because ultraviolet (UV) radiation can pass through the clouds and cause sunburn. In addition, UV rays reflect off surfaces like sand, snow, and cement. Snow can have up to 30 percent reflectance and cause severe sunburn without protection. The sun's rays can also penetrate clear water. Using different types of protection (shade or clothing plus sunscreen) is the best way to reduce sun exposure and the risk of sunburn and skin cancer.

Seek shade — Areas that are shaded receive less UV radiation and can reduce your chances of developing a sunburn. Trees, an umbrella, or a structure (eg, a porch or tent) can provide shade. Sunscreen is still recommended while sitting in the shade because your skin is exposed to some UV rays, particularly through reflection off other surfaces.

UV index — The ultraviolet (UV) index was developed to predict the risk of sunburn in an area on a given day based upon local weather conditions. It gives a number between 0 and 11+, in which 0 indicates no risk of sunburn, 10 indicates a very high risk, and 11+ indicates an extreme risk of sunburn. Some authorities recommend photoprotection when the UV index reaches 3. You can find information about the UV index online at www.epa.gov/sunsafety/uv-index-applications. The UV index is often given in weather forecasts. Skin color must also be considered when using the UV index to determine safe exposure times in the sun.

Significant importance is attached to ultraviolet A (UVA) as well as UVB to calculate the UV index, so it is important that we always choose a broadband sunscreen.

SUNSCREEN AND PROTECTIVE CLOTHING — The active ingredients of sunscreens work by scattering and/or absorbing ultraviolet (UV) rays. They can be inorganic mineral (eg, titanium oxide or zinc oxide) or organic chemicals. Sunscreen formulations (gels, lotions, and sprays) typically contain several active ingredients and often a mix of particulate and soluble agents. Chemical agents, of which there are numerous, include avobenzones, cinnamates, and new agents such as phenylene bis-diphenyltriazine.

The sun protection factor (SPF) is primarily, but not exclusively, an indicator of how much protection the sunscreen offers against ultraviolet B (UVB) rays. You should look for a sunscreen that is labeled as "broad spectrum," meaning it protects against both ultraviolet A (UVA) and UVB rays.

Most people do not apply enough sunscreen to achieve the SPF on the label and can therefore overestimate their level of protection, resulting in sunburn. People typically apply 20 to 50 percent of the amount needed to achieve the labeled SPF, with a commensurate reduction of SPF. Applying the sunscreen twice is a good way to achieve better protection.

What SPF is best? — The American Academy of Dermatology recommends that everyone use sunscreen that offers the following:

●Broad-spectrum protection (protects against UVA and UVB rays)

●SPF 30 or higher

●Water resistance

How much sunscreen do I need? — You should apply sunscreen generously to all exposed skin 20 minutes before exposure. Exposed skin is any skin that is not protected from the sun. The SPF is determined at an application thickness of 2 mg/cm² of skin, which means that good application is needed to achieve the labeled SPF. One approach is the "teaspoon rule," which means a generous teaspoon of sunscreen to each leg, the front torso, and back torso and a generous half-teaspoon to each arm, face, and neck. Applying less than this amount may reduce the sunscreen's SPF rating. Alternatively, applying the sunscreen twice is a good way to achieve better protection.

You should reapply sunscreen after sweating, rubbing the skin, drying off with a towel, or swimming. The traditional advice is to reapply sunscreen every two to three hours. However, reapplying sunscreen as soon as 20 minutes after going outside may offer greater protection, allowing you to completely cover areas that you might have missed when you first applied sunscreen. You should then reapply every two to three hours.

Protect your lips with lip balm containing an SPF of 30 or higher and reapply frequently. Some cosmetic products (eg, liquid foundation, lipstick) and moisturizers contain sun-protective ingredients, although to be truly effective, these products should be labeled as having an SPF of 15 or higher.

Sunscreen and vitamin D — Although UV radiation has many deleterious consequences, wavelengths within the UVB spectrum have the beneficial effect of triggering the production of vitamin D by the skin. This is the main source of vitamin D for most people, which is essential for good bone health. Field studies have shown that although correct sunscreen use protects against sunburn (primarily caused by UVB), it still allows very good vitamin D synthesis because the UVB dose for this is much lower than the dose for sunburn. Thus, the benefit of sunscreen use against sunburn and skin cancer is not compromised by any significant effects on vitamin D production.

Does sunscreen expire? — Manufacturers recommend throwing away sunscreen when it has passed the expiration date listed on the bottle. However, sunscreens can last longer than their recommended date, especially if they have been stored at room temperature. Use common sense to assess; if the sunscreen doesn't smell correct or if the consistency is not right, then discard. For sunscreen that does not have an expiration date, a typical recommendation is to replace it every season. Expired sunscreen may be less effective, potentially reducing the SPF rating and increasing your risk of sunburn.

Clothing — In addition to sunscreen, consider covering exposed skin with a wide-brimmed hat, long-sleeved shirt, and long pants. A hat made of tightly woven material (eg, canvas) can provide shade for the face, ears, and back of the neck.

Clothing made from tightly woven, dark fabric tends to provide greater protection than light-colored fabrics, although they may feel more uncomfortable as they absorb more UV, which gets converted to heat. Some manufacturers have sun-protective clothing with efficacy indicated as ultraviolet protection factor (UPF), which is essentially the same as SPF. In addition, UV-absorbing agents can be applied to clothing in the laundry.

Sunglasses that provide 100 percent UV ray protection can reduce your risk of cataracts (clouding in the eye's lens); wraparound glasses provide the most complete protection.

Tips for children — Children are at higher risk than adults for becoming sunburned because they are usually unaware of the risks of sunburn and are less likely to use preventive measures (eg, sunscreen, shade). Sunburn in childhood is also a risk factor for melanoma. Thus, regular sunscreen application is imperative for children. Baby formulas are recommended, as these are more likely to contain mineral blockers (eg, titanium dioxide or zinc oxide) that are less likely to be absorbed into the bloodstream.

Babies under six months should be kept out of direct sunlight, and mineral sunscreen can be applied to any exposed areas of the skin (eg, face and back of hands). Parents are encouraged to use hats, sunglasses, and shade to protect children from the sun.

SUN TANNING — A tan is the skin's response to molecular damage by ultraviolet (UV) radiation. Damage to deoxyribonucleic acid (DNA) is thought to be an important trigger. Tanning also increases the long-term consequences of sun exposure, such as skin cancer and wrinkling; habitually sun-exposed skin (eg, face) typically looks older than skin that is habitually sun protected (eg, buttock). People with darkly pigmented skin have a high level of the pigment melanin in their skin, which provides protection against DNA damage, sunburn, and skin cancer. Tanning increases your skin's production of melanin, which in people with lightly pigmented skin can provide very limited protection against further damage from UV radiation. This is equivalent to an SPF of 2 to 4. However, the small benefit of tanning (protection from sunburn) does not outweigh the risks (skin cancer, aged skin).

TANNING BEDS — The United States Department of Health and Human Services and the World Health Organization's International Agency of Research on Cancer panel have declared ultraviolet (UV) radiation from the sun and artificial sources, such as tanning beds and sun lamps, to be a known carcinogen (cancer-causing substance). Tanning beds primarily emit ultraviolet A (UVA) radiation as well as a small amount of ultraviolet B (UVB) radiation. Tanning beds can cause sunburn if exposure is not carefully monitored and have been linked to an increased risk of skin cancer, especially melanoma, a potentially deadly form of skin cancer.

Some countries have totally banned the use of commercial tanning lamps (eg, Australia, Brazil). Other countries restrict their use. In the United States, regulation varies from state to state, with age bans ranging from 14 to 18 years in many cases. Tanning beds should not be used by people under the age of 18 years and with exposure restrictions. Tanning beds should not be used by those with lightly pigmented skin. For those who do use tanning beds, it is particularly important to use protective eyewear when the sunlamp is on because the UV radiation from tanning beds may cause cataracts and melanoma of the eye.

SUNLESS TANNING — As people become more aware of the risks of skin cancer from sun exposure and tanning beds, sunless tanning products have become increasingly popular. A variety of safe and natural-appearing sunless tanning products are available, including lotions, gels, and sprays.

Topical tanning agents, such as dihydroxyacetone, combine with skin proteins to give a darker color. The staining is temporary, usually lasting less than one week unless you reapply the product, but does not provide any protection from sunburn.

No tanning pills or tanning accelerators taken by mouth have been approved by the US Food and Drug Administration (FDA). These are marketed to darken the skin by either stimulating the body's pigmentation system or distributing the color additives within the skin. However, their safety is questionable, and use is not advised.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Melanoma skin cancer (The Basics)
Patient education: Non-melanoma skin cancer (The Basics)
Patient education: Sunburn (The Basics)
Patient education: Actinic keratosis (The Basics)
Patient education: Keloids (The Basics)
Patient education: Melasma (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Sunburn (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Primary prevention of melanoma
Melanoma: Epidemiology and risk factors
Sunburn
Vitiligo: Pathogenesis, clinical features, and diagnosis
Selection of sunscreen and sun-protective measures

The following organizations also provide reliable health information.

●American Academy of Dermatology

(https://www.aad.org/public/everyday-care/sun-protection)

●National Library of Medicine

(https://medlineplus.gov/sunexposure.html, available in Spanish)

●Center for Disease Control and Prevention

     (https://www.cdc.gov/niosh/topics/sunexposure/sunburn.html)

●The National Cancer Institute

(https://progressreport.cancer.gov/prevention/sunburn)

●The Environmental Protection Agency

     (https://www.epa.gov/sunsafety)

●The Skin Cancer Foundation

     (https://www.skincancer.org/)

●The National Council on Skin Cancer Prevention

     (https://skincancerprevention.org/)

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