When I eat scallops or shrimp I get temporary hearing loss and a ringing in my ears. When my sister eats shellfish, she gets temporary "lockjaw," or an extreme pain in her "jaw joints." For both of us, this lasts 24-36 hours. We assume this is a food allergy and might be hereditary. But what is the underlying cause, why does this assumed allergy manifest itself differently in us -- and is it indeed hereditary?