Other factors affect this protection, such as the degree of sweating , swimming, and so forth. SPF 2 is for those who basically need no sunscreen. As the number increases, it can be used on those whose skin is more and more sensitive to sunlight. SPFs above 30 offer little increase in protection over SPF 30. Some ointment-based preparations such as zinc oxide are water repellent and stay on even during swimming.
Zinc oxide is ideal for the nose and ears while swimming.
A number of products give good UVB coverage. Waterproof formulations maintain sunburn protection for at least 80 minutes. Sweat-resistant formulations maintain sunburn protection after up to 30 minutes of heavy perspiration . Do not skimp. Reapply after swimming, sweating , or other activities that may result in the washing away or removal of the sunscreen.