What SPF 50 does not mean…
SPF 50 does not mean 50 minutes.
SPF 50 does not mean we reapply the sunscreen every 50 minutes.
SPF 50 does not mean the sunscreen’s effect lasts 50 minutes.
What does the 50 in SPF 50 mean…
To consumers, what the 50 in SPF 50 means is not obvious.
The 50 in SPF 50 means it blocks 98% of UVB radiation.
Blocking 98% of UVB radiation means it allows 2% of the sun’s UVB radiation to enter and affect the skin.
So, how long does SPF 50 last?
50 in SPF 50 does not indicate when the sunscreen should be reapplied.
All sunscreens should be reapplied every two hours, irrespective of their SPF number.