Final answer:
The first thing you should do when guests say they have a food allergy is to take their allergy seriously and gather more information about it.
Step-by-step explanation:
When guests say they have a food allergy, the first thing you should do is take their allergy seriously and ask them for more information about their specific allergy. It's important to understand what foods they are allergic to and how severe their allergy is. This will help you to make appropriate accommodations and avoid cross-contamination.