If Aquavit’s Marcus Samuelsson had judged last week’s cooking demo on Top Chef, he would have offered sound advice: Don’t eat something you’re allergic to just before you go on live television. At last night’s Food Allergy Ball, Samuelsson was honored with a Lifetime Achievement Award for developing a restaurant-staff training program, and spoke of his own food allergy. The chef is allergic to buckwheat, so visits to Matsugen (soba) or the Russian Tea Room (blinis) are out. A few years ago, Samuelsson nibbled on a piece of bread just before appearing on Good Morning Sweden. Minutes later, he realized he’d ingested buckwheat. “My whole system shut down in front of live TV,” he recalled, “I’m on the floor.” He took a pill during a commercial break and waited a half hour before he could resume the demonstration. Aquavit servers now ask every diner if they have any food allergies, Samuelsson said. “I consider it a blessing because I put myself in the mind of the customer right away.”