Lake living means you’ll be spending plenty of time in the sun. Water can reflect the sun’s damaging rays onto your skin and wash off sunscreen more quickly. Also, swimsuits and summer clothes offer much less protection from the sun. So, it’s important to make sure to protect yourself and your family when you’re spending time outside. But what is SPF exactly and what should you look for in sun protection?

What is SPF?

SPF stands for ‘Sun Protection Factor.’ It measures how well a sunscreen can protect against the sun’s UVB rays. The number of a suncreen’s SPF tells you how many times longer you should be able to stay out in the sun before your skin begins to burn. For example, if your skin normally begins to redden after 10 minutes of being in direct sunlight, an SPF 15 would theoretically allow you to stay in the sun for 150 minutes (15 times) before showing signs of damage. It’s important to note this is a rough estimate and that it only communicates the UVB protection sunscreen offers.

What is the Difference Between UVB and UVA Rays?

The sun emits both UVB and UVA rays. Sunscreen SPF measures protection against UVB rays because those are the most dangerous. UVB rays are responsible for damaging skin’s surface–causing it to burn. UVA rays account for 95% of UV radition. While they have lower radiation energy, they penetrate to the deeper lays of skin.

What is ‘Broad Spectrum’ Sunscreen?

‘Broad Spectrum’ protection means that the sunscreen has a combination of ingredients known to protect against both UVB and UVA rays. Both types of UV rays contribute to skin cancer and cause premature aging. So, it’s important to look for ‘Broad Spectrum’ sunscreen that protects against UVA rays as well, regardless of the SPF–which only protects measures protection against UVB rays.

Is a Higher SPF Better?

There is a common misconception that higher SPFs offer significantly better protection. As mentioned above, SPF is a measure of the time it takes before skin begins to burn. It indicates what percentage of the sun’s UVB rays are blocked. However, the SPF scale is not linear:

SPF 15 offers 93% protection against UVB rays
SPF 30 offers 97% protection
SPF 50 offers 98% protection

A higher SPF provides better protection, but not significantly.

When it comes to protecting your skin, most dermatologists recommend finding a Broad Spectrum Sunscreen with SPF 30 and being diligent about applying every couple hours.