There are many reasons why you may still be getting some tan despite diligent use of sunscreen. One likely cause is the fact that even the best of sunscreens still let some sun rays through. A high SPF number is not about better or deeper protection, but only longer protection—an SPF 30 means you can stay in the sun 30 times longer than it would normally take you to get a slight burn. For most skin types that would provide over 18 hours of sun exposure without getting sunburned. That’s impressive, but it is also only a measure of the length of time the protection lasts.

High SPF numbers give the false impression they can provide enhanced protection when that is not the case. A well-formulated sunscreen with an SPF 30 still only protects your skin from about 97% to 98% of the sun’s rays. That means 2% to 3% of the sun’s rays are still getting through, and that can trigger melanin production, the skin’s tanning response. This is especially true for those with darker skin tones or for those who have a lot of previous sun damage, because for them hypermelanin production is more likely to take place.

Here is a chart to give you an idea of the numbers:


SPF 2 50% UV protection
SPF 4 70% UV protection
SPF 8 88% UV protection
SPF 15 94% UV protection
SPF 30 97% UV protection
SPF 50 98% UV protection
SPF 70 98% UV protection

Further, most people misunderstand or have poor information about how to get the best sun protection. Please review the “Applying Sunscreen” and “Sun Strategy” sections in this chapter. It is essential to apply sunscreen liberally and to be sure that the active ingredients on the label include one of the UVA-protecting ingredients: avobenzone, butyl methoxydibenzylmethane, Tinosorb, ecamsule (Mexoryl), titanium dioxide, or zinc oxide.