Popular Reese's treats rely on a butane derivative linked to cell damage, immune suppression, and potential cancer risks.

What We Found

The ingredient is real. Hershey's label for Reese's Peanut Butter Cups lists "TBHQ & citric acid (to maintain freshness)." TBHQ (tert-butylhydroquinone) is an antioxidant preservative that slows fats from going rancid.

"Butane derivative" is a stretch. TBHQ isn't butane; the name comes from its tert-butyl group, a small carbon group related to butane.

What regulators say: the FDA allows TBHQ at no more than 0.02% of a food's oil or fat (21 CFR 172.185, in place since 1977). A long-term National Toxicology Program feed study (1997) found no evidence of carcinogenic activity in rats or mice. TBHQ is not on the FDA's current list of chemicals under review (related preservatives BHA and BHT are).

Why some groups worry: the Environmental Working Group recommends limiting TBHQ, citing rodent studies linking it to weaker natural killer (immune) cells and to DNA damage at higher doses, plus a 2021 EWG-led study flagging it as a possible immunotoxin. Human evidence is limited, and many animal doses are far above typical diet levels.

Sources

1. Hershey's, Reese's Peanut Butter Cups ingredients (opens in new tab)
2. FDA rule on TBHQ, 21 CFR 172.185 (opens in new tab)
3. National Toxicology Program, TR-459 (TBHQ feed studies) (opens in new tab)
4. FDA, chemicals under review (opens in new tab)
5. EWG on TBHQ (opens in new tab)
6. Naidenko et al. 2021 (EWG-led, peer reviewed) (opens in new tab)