Sun Exposure

Increased exposure to ultraviolet (UV) radiation occurs near the equator, during summer months, at high elevation, and between 10 am and 4 pm. Reflection from the snow, sand, and water increases exposure, a particularly important consideration for snow skiing, beach activities, swimming, and sailing. In addition, several common medications may cause photosensitivity reactions:

  • Acetazolamide
  • Amiodarone
  • Antibiotics (fluoroquinolones, sulfonamides, and tetracyclines)
  • Diuretics (furosemide, hydrochlorothiazide)
  • Nonsteroidal anti-inflammatory drugs (celecoxib, ibuprofen, ketoprofen, naproxen, piroxicam)
  • Sulfonylureas (glipizide, glyburide)

Medical conditions such as connective tissue diseases, polymorphous light eruption, rosacea, and vitiligo can increase sun sensitivity. Alcohol consumption can lead to behavioral changes that increase the risk of sunburn.

Both UVA rays (320–400 nm) and UVB rays (290–320 nm) are carcinogenic. UVA rays are present throughout the day and can pass through window glass. UVA rays cause premature aging of the skin and are primarily responsible for drug-related phototoxicity and photoallergic reactions. UVB rays are most intense from 10 am to 4 pm, are blocked by window glass, and are most responsible for sunburn.

Serious burns are painful, and the skin may be red, tender, swollen, and blistered. These sunburns may be accompanied by fever, headache, itching, and malaise. Cumulative overexposure to the sun leads to premature aging of the skin, including wrinkling and age spots, as well as an increased risk for skin cancer, including basal cell carcinoma, squamous cell carcinoma, and melanoma. Repeated exposure to sunlight in the eyes can also result in ocular pterygium formation, cataracts, and macular degeneration.


Avoid Overexposure to the Sun

Sun exposure is the most preventable risk factor for skin cancer, including melanoma. Staying indoors or seeking shade between 10 am and 4 pm is very important in limiting exposure to UV rays, particularly UVB rays. The intensity of UV rays varies seasonally, peaking at the solstice, and gets stronger at the equator and at high altitudes. Be aware that sunburn and sun damage can occur even on cloudy days. Sunburn can occur in a fair-skinned person after as little as 10–15 minutes of unprotected sun exposure. Tanning beds and sun lamps are also carcinogenic and should be avoided.

Protective Clothing

Wide-brimmed hats, long sleeves, and long pants protect against UV rays. Tightly woven clothing and darker fabrics provide additional protection. High-UPF (ultraviolet protection factor >30) clothing is recommended for travelers at increased risk of sunburn or with a history of skin cancer. This type of clothing contains colorless compounds, fluorescent brighteners, or treated resins that absorb UV rays. Sunglasses that provide 100% protection against both UVA and UVB radiation are strongly recommended.


Sun protection factor (SPF) defines the extra protection against UVB rays that a person receives by using a sunscreen. Although higher-SPF sunscreens provide more protection than lower-SPF sunscreens, SPF is not linear. An SPF 30 sunscreen does not offer twice the protection of SPF 15. Sunscreens with at least an SPF of 15 and that offer protection from both UVA and UVB rays (labeled “broad-spectrum SPF”) are recommended for best protection.

Physical sunscreens contain titanium dioxide or zinc oxide, inorganic molecules that are confined to the stratum corneum and reflect and scatter both visible and UV light. They are effective, broad-spectrum sunscreens that protect against both UVA and UVB radiation. With the advent of nanotechnology, these products no longer cause an opaque white film on the skin and have become cosmetically acceptable for widespread use. They are recommended for people who burn easily or who take medications that may cause photosensitivity reactions.

Chemical sunscreens absorb rather than reflect UV radiation. A combination of chemical agents is recommended to provide broad-spectrum protection against UVA and UVB rays. The Food and Drug Administration (FDA) recommends using sunscreen with 15 SPF or higher regularly and as directed.

Travelers should consider the following key points regarding physical and chemical sunscreens:

  • Choose a broad-spectrum sunscreen with ≥15 SPF to ensure adequate UVA and UVB protection.
  • For UVA protection, look for the following active ingredients: zinc oxide, titanium dioxide, avobenzone, ecamsule, oxybenzone, dioxybenzone, or sulisobenzone.
  • Select a waterproof or water-resistant product. Waterproof sunscreens confer approximately 80 minutes of protection in the water, and water-resistant products offer 40 minutes of protection.
  • Apply to dry skin 15 minutes to one-half hour before exposure to the sun.
  • At least 1 oz (2 tablespoons or enough to fill a shot glass) of sunscreen is needed to cover the exposed areas of the body. Most people only apply 25%–50% of the recommended amount of sunscreen, which decreases the achieved SPF.
  • Apply to all exposed areas, including the ears, scalp, back of the neck, tops of the feet, and backs of the hands.
  • Use a lip balm or lipstick with broad-spectrum SPF ≥15.
  • Reapply every 2 hours and after sweating, swimming, or towel-drying (even on cloudy days).
  • The FDA requires that all sunscreens retain their original strength for at least 3 years. Always check the expiration date and discard all expired product.
  • Sunscreens should be applied to the skin before insect repellents. (Note: DEET-containing insect repellents may decrease the SPF of sunscreens by one-third. Sunscreens may increase absorption of DEET through the skin.)
  • Avoid products that contain both sunscreens and insect repellents, because sunscreen may need to be reapplied more often and in larger amounts than the repellent.


Travelers with sunburn should maintain hydration and stay in a cool, shaded, or indoor environment. Topical and oral nonsteroidal anti-inflammatory drugs decrease skin redness if used before or soon after sun exposure and may relieve symptoms such as headache, fever, and local pain. Pain is usually most intense 6–48 hours after sun exposure, and skin usually peels 4–7 days later. Topical steroids are of limited benefit, and systemic steroids appear to be ineffective in alleviating pain. Cool compresses, colloidal oatmeal baths, moisturizing creams, and topical aloe vera gel may relieve symptoms. Oral diphenhydramine may relieve itching. If blisters occur, they should be left intact to promote faster healing. Open erosions should be coated with petroleum jelly and covered with sterile gauze to decrease the risk of infection. If infection occurs, oral antibiotics may be necessary. In severe cases of sunburn, dehydration and hypovolemia may occur, presenting with severely inflamed or reddened skin, disorientation, dizziness or fainting, nausea, chills, high fever, and headache. Hospitalization for intravenous rehydration and narcotic analgesics for pain relief may be required in these extreme cases.


  1. Gu X, Wang T, Collins DM, Kasichayanula S, Burczynski FJ. In vitro evaluation of concurrent use of commercially available insect repellent and sunscreen preparations. Br J Dermatol. 2005 Jun;152(6):1263–7.  [PMID:15948991]
  2. Han A, Maibach HI. Management of acute sunburn. Am J Clin Dermatol. 2004;5(1):39–47.  [PMID:14979742]
  3. Henry WL, Steven QW. The Skin Cancer Foundation’s Guide to Sunscreens New York: Skin Cancer Foundation; 2012 [cited 2016 Sep. 22]; Available from:
  4. Krakowski AC, Kaplan LA. Exposure to radiation from the sun. In: Auerbach PS, editor. Wilderness Medicine. 6th ed. Philadelphia: Mosby Elsevier; 2012. pp. 294–313.
  5. McLean DI, Gallagher R. Sunscreens. Use and misuse. Dermatol Clin. 1998 Apr;16(2):219–26.  [PMID:9589195]
  6. Wang SQ, Stanfield JW, Osterwalder U. In vitro assessments of UVA protection by popular sunscreens available in the United States. J Am Acad Dermatol. 2008 Dec;59(6):934–42.  [PMID:18835064]
  7. Wang SQ, Tooley IR. Photoprotection in the era of nanotechnology. Semin Cutan Med Surg. 2011 Dec;30(4):210–3.  [PMID:22123418]


Vernon E. Ansdell, Rodd Takiguchi