Five prinicples of sunscreen

Sun is the main source of ultraviolet light that is divided into UV-A, UV-B and UV-C based on wave-length. UV-C is mostly blocked by ozone before reaching earth surface. UV-A and UV-B are most dangerous and cause aging as they penetrate ozone and skin damaging its tissues and cells. Most sunscreens only block UV-B which causes sunburn. However it is recommended to use products with broad-spectrum coverage against both UV-A and UV-B. Protection from sun-light using sunscreen is an efficient way to avoid its UV light toxicity and damage to skin. Five principles to achieve best results are the followings.

    1. Choose the right sunscreen
      • A sunscreen with higher SPF (Sun Protection Factor) provides a higher protection against sunburn. Sunscreen with SPF greater than 30 is most recommendable and SPF less than 15 does not protect enough.
      • Expired sunscreens are less effective therefore it is better to pay attention to their expiration date.
    2. Apply cream generously
      • 30 grams / 1 ounce to cover whole body
      • 3 grams to cover face, neck, and hands
    3. Apply frequently preferably daily
      • Ultraviolet light is not visible and UV radiation in a partially cloudy day can be high. Even if the visible sun light is not intense, UV radiation can be similar to a sunny day. Indirect UV radiation reflected from water, sand, and snow can still be very high especially between 10AM to 4PM and still damage skin even staying in shadow.
    4. Apply 30 minutes before sun exposure
      • This time allows the sunscreen to penetrate epidermis (the outer layer of skin). Otherwise it can be simply wiped from body by cloths or in contact with other surfaces.
    5. Reapply
      • Every 2 hours
      • After swimming, sweating, or drying off with towel
      • Even water resistant products last 40 minutes and maximum 80 minutes if very resistant and need to be reapplied.