SPF, or "sun protection factor", is a measurement of how much the sunscreen shields a person from ultraviolet B rays (UVB). These are the rays that cause sunburn. Sunscreen with an SPF of 30 offers protection from 96.7% of UVB rays, while sunscreen with an SPF of 50 offers protection from 98% of UVB rays. So higher SPFs offer only marginal improvement in protection.

More importantly, SPF does NOT measure the ability of the sunscreen to protect users from ultraviolet A rays (UVA). UVA rays penetrate more deeply into the skin than UVB rays and lead to the premature aging of skin (the early development of wrinkles) and increase the risk of developing skin cancer. It is possible to have a sunscreen with SPF100 and still have little or no protection from UVA rays.

Unfortunately, people who use high-priced sunscreens may not use as much, nor apply it as frequently as they should. And they may be less willing to share it with their family and friends.

Here are some basic tips on selecting a sunscreen.

• Select a sunscreen with an SPF of 15 and higher. You can ignore SPF values over 50.
• Select a sunscreen with UVA protecting ingredients, such as avobenzone or Mexoryl SX.
• Select a sunscreen labeled “very water resistant” or “waterproof”. (The term “waterproof” may be phased out because it is considered somewhat misleading)
• Find a brand that fits your budget.

Consumer Reports provided high ratings for the following brands:

• Blue Lizard Regular Australian SPF 30+
• Mustella Bébé/Enfant High Protection SPF 50
• Lancôme Paris Sôleil Ultra Expert Sun Care for Sensitive Skin SPF 50
• Fallene Cotz SPF 58

Remember to discard sunscreen that is more than two years old because it might have lost its potency.

Learn more about sunscreens.

The most alarming results showed that 31% never wear sunscreen.

And although children are very susceptible to the long-term consequences of sun exposure, 27% of parents with kids under 12 years of age never or only sometimes apply sunscreen on their children when they are outside for 2 to 4 hours (14% of parents don’t even apply it to their kids when their children will be outside for more than 4 hours.)

Fortunately, the importance of sunscreen use been has been taken to heart by some, primarily women. When planning to spend 2 to 4 hours in the sun, 48% of women reported being likely to wear sunscreen vs. 27% of men.

Unfortunately, the damaging effects of the sun can be forgotten over time, particularly at the end of a long winter. 48% of sunscreen users who experienced a sunburn in the last 2 years said it happened during their first time out in the sun after months of little or no sun. 

A separate study of sunscreen use in Australia showed that most adults used only about ½ of the recommended amount of sunscreen on their bodies. If people apply only ½ of the sunscreen, they will get only ½ of the protection.

So most of us could be doing better. Here are some basic tips on using sunscreen

• Apply sunscreen regularly
• Don’t’ skimp on sunscreen! Most adults need 2 to 3 tablespoons (one ounce) to cover most sun-exposed areas.
• Apply sunscreen 15 to 30 minutes before going out in the sun. It does not have protective effects until it has absorbed and reacted with the skin.
• Reapply sunscreen every 2 hours or after swimming or sweating heavily.
• Don't rely on sunscreen alone to protect you from skin cancer. Wear tightly woven clothing and a hat, limit sun time, and seek shade during the hottest hours of the day.