When to wear Sunscreen?
 
Since most ultraviolet damage is incidental and is not restricted to sunbathing, it is wrong to believe you do not need sunscreens simply because you do not sunbathe.

The need for sunscreens will vary with your skin, your activities, where you live, and your climatic conditions. For example, a fair skinned individual living in the southern United States should apply sunscreens several times a day In northern Canada, however, daily use of sunscreens may be necessary only during the summer months or when taking part in outdoor winter sports such as skiing, skating, or tobogganing. Remember, ultraviolet light is reflected from sand, sun, water, snow, and ice. Remember, too, that a body immersed in water is not protected.

Daily-wear moisturizers with SPF (non-recreational) typically use the same oilbased sun filters used in recreational products, but typically do not incorporate the polymeric film formers used for waterproofing purposes. In addition, since wash resistance is not a critical performance criterion, water-soluble filters can be more readily incorporated into these types of products. Providing UV protection into both the water and oil portions of the emulsion can help fill in the “holes” left by evaporation of water in an “oil filter only” sunscreen product.

The frequency with which sunscreens should be applied varies with your activities. If you work in an office building all day, then an application first thing in the morning would be adequate. If you work out of doors, however, whether in winter or summer, several applications of high SPF sunscreens throughout the day would be necessary. You should remember that longer ultraviolet rays (UVA) can pass through glass. Broad spectrum sunscreens, therefore, should be worn if you spend a fair amount of time in the car or work close to a window during the day.