Q: My girlfriend has confirmed allergies to tuna, anchovies, shrimp, crab, clams and mussels. However, she can eat salmon with no issues. Does it make sense that she could be able to eat salmon but still be allergic to virtually every other creature of the sea? If so, could she consider trying squid or escargot?
Dr. Waserman: It is confusing, but it does make sense. The foods you mentioned can be broken down into two groups: fish and shellfish. The main allergens in these groups are different, and allergy can develop to either group and, in rare cases, to both. It is also possible to be allergic to some but not all types of fish or shellfish within each group. For example, there are those who can eat crab but not lobster, while others can eat salmon but not cod. There is, however, a high degree of cross-reactivity within each of these food groups, and some may need to avoid all forms of fish or shellfish.
Given your girlfriend’s high degree of reactivity to many members of the fish and shellfish family, I would not recommend experimentation with any new “creature of the sea” until she is assessed by her allergist.
She also needs to be careful eating salmon when dining out. There is a risk of cross-contamination if her salmon is prepared on equipment (for example, a frying pan) where other fish or shellfish are prepared.
Dr. Susan Waserman is an allergist and Professor of Medicine in the Division of Allergy and Clinical Immunology at McMaster University in Hamilton, Ont. She is also a past president of the Canadian Society of Allergy and Clinical Immunology.