It provide about 96.7 % protection from UVB-radiation or in other words, they allow to stay about 30 times longer in the sun before an erythema (sun burn) will develop. Since the thermal radiation of the sun (infrared) is quite stressful for the skin it is recommended to expose the skin in moderation despite the sun screen. Excessive sun exposure is a serious health threat. Particularly babies and toddlers should not be exposed to direct sun light.