Background The US Food and Drug Administration (FDA) requires a warning label on nicotine e-cigarettes and pouches: ‘This product contains nicotine. Nicotine is an addictive chemical’. Some brands marketing synthetic nicotine products have modified the warning (‘This product contains tobacco-free nicotine (TFN)…’). The public health impact of altering the warning is unknown, so we examined its impact on risk perceptions and use intentions.

Methods 1000 participants completed an anonymous online survey. Participants viewed the black-and-white FDA and TFN-modified warning labels in isolation, in a randomised order and reported on perceived addictiveness and, secondarily, use intentions. Participants then selected which label conveyed the most harm overall. Generalised estimating equations (GEEs) were used to evaluate the impact of label type and participant characteristics on perceived addictiveness and, secondarily, use intentions. Multivariable logistic regression was used to evaluate relationships between participant characteristics and choosing which label conveyed the most harm.

Results Overall, the TFN-modified label was associated with lower addictiveness ratings but not increased use intentions. Where significant interactions between label type and participant characteristics emerged, TFN-modified labelling was associated with disproportionately reduced risk perceptions or increased use intentions among vulnerable populations (eg, underage individuals, racially minoritised groups). 25.5% of participants selected the TFN-modified label as conveying the most harm, with younger individuals (<21 years) significantly less likely to choose the TFN-modified label.

Conclusions Modifying the FDA-mandated nicotine warning label to include ‘tobacco-free nicotine’ may negatively impact public health, so the FDA should enforce inclusion of its original required warning label.