The SPF 'Booster' Debate: Is Butyloctyl Salicylate Padding the Numbers?
Some sunscreens post eye-catching SPF lab numbers partly thanks to 'booster' additives — here's what butyloctyl salicylate is and why it's controversial.
EWG's 2025 guide singled out SPF 'boosters' such as butyloctyl salicylate (BOS), arguing they can inflate a product's measured SPF in testing without genuinely improving broad-spectrum UVA/UVB protection — a claim that drew industry pushback.
EWG contends that an SPF number padded by boosters can overstate real-world protection, while industry voices counter that such ingredients have legitimate formulation roles and that finished-product SPF testing reflects actual performance.
Questions we get a lot
What is butyloctyl salicylate (BOS)?
BOS is an ingredient used in some sunscreens that EWG describes as an SPF 'booster.' It is not itself an approved standalone UV filter in the U.S., but EWG argues it can raise a product's measured SPF in testing. Its exact role in finished-product performance is part of the current debate.
Does an SPF booster mean my sunscreen is less protective?
EWG's concern is that a boosted SPF number may not reflect proportionally better broad-spectrum protection, especially against UVA. Industry disputes this. What's clear is that the SPF figure alone doesn't tell you about UVA coverage, so look for 'broad spectrum' labeling regardless.
How does EWG decide a product relies on boosters?
EWG's published methodology lays out how it assesses sunscreens, including its scrutiny of ingredients it considers SPF boosters. Critics in the industry argue the approach overstates the issue. Reading EWG's methodology directly is the best way to judge how much weight to give its booster claims.
r/SkincareAddiction: 'Butyloctyl salicylate keeps showing up in my sunscreens — is it a real UV filter or just there to game the SPF test?'