The LookOut  
Health News  A service of Saint John's Health Center

Ask the Doctor at Saint John’s: Shedding Light on Fun in the Sun

Q: Will sunscreen protect me for as long as I want to stay in the sun?

A: By Alison Garb, M.D., staff internist at Saint John’s Health Center

Protecting your skin, whenever it’s exposed to the sun, is extremely important. Wearing sunscreen is a start.

However, even if you’re using sunscreen, do not stay in the sun for extended periods of time. Sunscreen does not provide complete protection from the sun’s ultraviolet (UV) rays. Also, make sure you’re using sun protection products correctly, and be aware of their limitations.

The SPF classification on sunscreen refers to Sun Protection Factor. To determine how long to stay in the sun using a SPF simply multiply a product’s SPF value by the length of time it normally takes you to get burned without any sun protection.

For example fair-skinned people begin to burn in about 15 minutes on a sunny day. If you’re using SPF 15 sunscreen, multiply that number (15) by the number of minutes before burning (15). That means 225 minutes – or 3 hours, 45 minutes – of protection. But sunscreen products aren’t necessarily that exact, and several hours of exposure to the sun’s UV rays is a very long period.

Furthermore, there are some major assumptions when talking about the length of protection sunscreen provides. First, that you’re applying the sunscreen before you go outside. Second, that you’re covering all exposed areas. Third, that you’re continuously reapplying the sunscreen. These are fairly simple steps to take. Nevertheless, they require a proactive approach.

Adults should be using about an ounce of sunscreen to cover arms, legs, face, hands, neck and ears. Also, “water resistant” sunscreen – even though made to protect you when swimming or sweating – may only last about 40 minutes. If you’re coming out of the water and towel drying, lotion can rub off.

When outdoors, seek shady areas. Wear protective clothing as well. Any clothing – say, a T-shirt over a bathing suit – is better protection than no coverage. But that white cotton T-shirt? It may only be providing as much protection as SPF 4 sunscreen. Dark colors and tight weaves are preferable.

Still, covering up only works on those areas actually covered. A wide-brimmed hat, as well as UV protection sunglasses to protect your eyes, are both very useful. But if the backs of your hands are unprotected – they’re just that: unprotected.

Apply and reapply sunscreen, wear protective clothing, don’t stay out for extended periods of time and seek the shade. These are all steps you can take to protect your skin from the sun’s UV rays and enjoy a lifetime of active living in Southern California.

Dr. Garb is a staff internist at Saint John’s Health Center. For more information about Dr. Garb or other Saint John’s services, please call (310) 829-8990 or visit the website at For a physician referral or a second opinion, please call 1-888-ASK-SJHC.

Want to learn about a variety of health and lifestyle issues? Watch “Coffee Break,” a weekly, live television show broadcast Wednesdays at 2:00 – 3:00 p.m. on Santa Monica City TV Channel 16 and LA City TV Channel 36.

Health News is provided by Saint John's Health Center and covered under their copyrights