Airline carriers have a long tradition of serving peanuts on flights, and often serve little else. But the practice also presents a challenge to travellers with severe nut allergies, who can suffer a reaction simply by touching a surface that has been exposed to nuts. Tensions between passengers with food allergies and airline staff members have risen in recent years, as airlines have begun to enforce stricter rules related to preboarding passengers. In the past, parents of young children could board the plane early, giving them a chance to wipe down seats, trays and armrests to reduce exposure to allergens. But today many airlines have stopped letting families with children board before other passengers. Now families with nut allergies are waging a legal challenge against such policies. <br/>