BACKGROUND: Mandatory labeling of products with top allergens has improved food safety for consumers. Precautionary allergen labeling (PAL), such as "may contain" or "manufactured on shared equipment," are voluntarily placed by the food industry. OBJECTIVE: To establish knowledge of PAL and its impact on purchasing habits by food-allergic consumers in North America. METHODS: Food Allergy Research & Education and Food Allergy Canada surveyed consumers in the United States and Canada on purchasing habits of food products featuring different types of PAL. Associations between respondents' purchasing behaviors and individual characteristics were estimated using multiple logistic regression. RESULTS: Of 6684 participants, 84.3% (n = 5634) were caregivers of a food-allergic child and 22.4% had food allergy themselves. Seventy-one percent reported a history of experiencing a severe allergic reaction. Buying practices varied on the basis of PAL wording; 11% of respondents purchased food with "may contain" labeling, whereas 40% purchased food that used "manufactured in a facility that also processes." Twenty-nine percent of respondents were unaware that the law requires labeling of priority food allergens. Forty-six percent were either unsure or incorrectly believed that PAL is required by law. Thirty-seven percent of respondents thought PAL was based on the amount of allergen present. History of a severe allergic reaction decreased the odds of purchasing foods with PAL. CONCLUSIONS: Almost half of consumers falsely believed that PAL was required by law. Up to 40% surveyed consumers purchased products with PAL. Understanding of PAL is poor, and improved awareness and guidelines are needed to help food-allergic consumers purchase food safely.