I received this excellent question during a patient’s consultation last week. She asked:
Doctor, if I wear a sunscreen with SPF50 in the morning, let say 8AM, I don’t need to reapply when I head out for lunch at 12PM, since I am already being protected by SPF50. It will never reach the length of time it takes to suffer from sunburn. Am I right?
Her question gets right to the heart of the conflicting and confusing messages we hear about sun protection. In reality, the effectiveness still depends on duration of exposure, time of the day, location, weather etc.
Here are a few fun facts to know:
1. SPF aka sun protective factor, measures the ability of a product to protect skin against sun’s ray.
2. The higher the SPF, the minimal increase of UVB protection it becomes. For example, SPF50
protect 98% of UVB, anything that is higher than SPF50 will not make much difference.
3. SPFs mainly measure UVB protection.
4. High SPFs only protect you from getting sunburn by UVB, but it does not mean it protects you
from UVA. UVA is the culprit which penetrates deep into your skin causing collagen breakdown,
ageing and wrinkles.
5. It is important that your sunblock protects you from both UVA and UVB.
6. Apply sunscreen more frequent if you sweat a lot or after a swim. Ideally every 4 hours.
One thing to remember is that:
It doesn’t matter if you are not using any skin care products but never leave home without a sunscreen!!