SPF 30 vs 50: does the difference matter?

Hold the floor: broad-spectrum SPF 30 minimum, every day on exposed skin.
Apply the tested amount: a shot glass for the body, a finger-length for the face.
Reapply on the clock: every two hours, after swimming or sweating - whatever the number.
Get seen if: you burn despite correct use, or a mole is changing - that is a dermatology visit, not a higher SPF.

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Mathematically, almost nothing: the American Academy of Dermatology notes SPF 30 blocks 97% of UVB rays, and a dermatologist at UT Dell Medical School lays out the full ladder - SPF 15, 30, 50, and 100 block 93%, 97%, 98%, and 99% respectively. Doubling the SPF number does not double the protection; it shaves one percent. But there is one practical argument for 50, and it is you: most people apply only a fraction of the tested amount - the AAD cites 20 to 50% - so real-world SPF 30 can behave like SPF 20, and starting higher buys margin against under-application. The traps: high SPF lasts exactly as long as low SPF - reapply every two hours regardless - and the false-confidence effect, where a bigger number licenses longer sun exposure, erasing the gain. The AAD floor is SPF 30, broad spectrum. Below that is under-protecting; above 50 is marketing; the shot-glass amount and the two-hour reapply are the variables that actually decide your burn.

SPF 30 vs 50: does the difference matter?

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