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.
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- 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.
- Apply cream generously
- 30 grams / 1 ounce to cover whole body
- 3 grams to cover face, neck, and hands
- 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.
- 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.
- 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.
- Choose the right sunscreen