Apply your sunscreen thoroughly or risk having your SPF protection cut in half

I use Hamilton SPF 80 for my sunscreen and I ensure that a total spread of it all over my body. I’m not surprised that a good 5-10 minutes is spent on putting my sunscreen. Why the need to thoroughly apply the lotion?

Well wearing sunscreen is smart, but if you don’t apply it correctly, your SPF protection is cut in half!

The dose used in FDA sunscreen testing is 2 mg/cm² of exposed skin. Provided one assumes an “average” adult build of height 5 ft 4 in (163 cm) and weight 150 lb (68 kg) with a 32 in (82 cm) waist, that adult wearing a bathing suit covering the groin area should apply 29 g (approximately 1 oz) evenly to the uncovered body area. Considering only the face, this translates to about 1/4 to 1/3 of a teaspoon for the average adult face. Larger individuals should scale these quantities accordingly.

Contrary to the common advice that sunscreen should be reapplied every 2–3 hours, some research has shown that the best protection is achieved by application 15–30 minutes before exposure, followed by one reapplication 15–30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, or rubbing/wiping