SPF measures the level of protection a sunscreen provides against UVB rays, which are the primary cause of sunburn and skin cancer. The higher the SPF number, the greater the level of protection.
Previously it was thought that the number on SPF indicated how often you need to reapply suncream, if you burn in 10 minutes than an SPF of 15 would give you 150 mins protection before reapplying and an SPF of 30 would give you 300 mins before needing to reapply. This is not the case.
As a rule of thumb, an SPF 30 sunscreen will block 97% of UVB rays, while an SPF 50 sunscreen will block 98% of UVB rays.
It is important to note that SPF only measures UVB protection and does not indicate protection against UVA rays, which can also cause skin damage. Look for sunscreens that offer broad-spectrum protection, meaning they protect against both UVA and UVB rays.
Another factor to consider is your skin type. Individuals with fair skin or a history of skin cancer may require a higher SPF level than those with darker skin. It is recommended to use a minimum of SPF 30 for daily use and SPF 50 for extended outdoor activities.
It is also important to apply sunscreen correctly and reapply every two hours or after swimming or sweating. Remember to apply sunscreen to all exposed areas, including your face, neck, and ears!