​Sun Protection Factor (SPF) is an index to indicate the degree of protection from ultraviolet B (UVB), the type of ultraviolet radiation that is more likely to cause sunburn. The higher the SPF, the longer the duration of the protection. A sunscreen with SPF 30 or higher should be applied frequently to maintain protection.

• Dry your skin well before applying the sunscreen.
• Apply the sunscreen at least half an hour before going into the sun.
• Apply the sunscreen generously and evenly over the exposed areas of the whole body.
• Wait for the sunscreen to dry before putting on your clothes or makeup.
• With a non-water resistant sunscreen, re-apply after every swim or after heavy perspiration but make sure your skin is dry first.
• With a water resistant sunscreen, re-apply every two hours or re-apply every hour if you have been swimming.
• Use sunscreen even on cloudy or overcast days. The sunrays are as damaging to your skin on hazy days as they are on sunny days.
• Use sunscreen with SPF of 30 or higher during high altitude activities such as skiing and mountain climbing. At high altitudes, there is less atmosphere to absorb the sunrays, so exposure to the sunrays is higher and the risk of your skin burning is higher.