Ask the allergist – Your questions answered – November 2021

November 4, 2021

Dr. Julia Upton
Dr. Julia Upton

Ask the allergist is a regular feature in our newsletters where Canadian allergists answer your questions! 

Dr. Julia Upton is on staff at the Hospital for Sick Children in the Immunology and Allergy Department; and an Associate Professor in the Department of Paediatrics at the University of Toronto. She is the past Section Chair of the Anaphylaxis and Food Allergy Section of the Canadian Society of Allergy and Clinical Immunology. Dr. Upton is also a member of our Healthcare Advisory Board

Please note: Dr. Upton is answering as an individual allergist and her answers do not constitute an official position of her affiliated organizations. Her responses are for informational purposes only and do not constitute specific medical advice, recommendations, diagnosis, or treatment. Please talk to your doctor about any concerns or questions you may have regarding your own health or the health of your child. 

This month she answers a question about adult-onset fish allergy. 


Fresh salmon steak with a variety of seafood and herbs. On black rustic background

I grew up eating different types of fish and now at age 32, I’ve been diagnosed with a fish allergy. Why is this and what do I need to know to manage it? 

Food allergy is often thought to be a concern of children but adults can have food allergies and they can develop new food allergies too. Sometimes with adults, it involves foods that have been eaten in the past without incident. 

Fish and shellfish are usually described as the most common adult-onset food allergies. Examples of fish are trout and salmon, while crustaceans (e.g., lobster, shrimp, crab) and molluscs (e.g., scallops, clams, oysters, mussels) are sometimes collectively referred to as shellfish. Additionally, fish, crustaceans and molluscs are sometimes collectively described as seafood. 

Adults who develop a food allergy are typically atopic, meaning they have other allergic conditions such as environmental allergies to pollen, dust mites, pets, etc. 

Adults can develop an Immunoglobulin E (IgE) mediated food allergy, in which symptoms result from the body’s immune system making antibodies called IgE. This kind of allergy can lead to anaphylaxis. 

To manage an IgE mediated allergy, you will need education about the condition, be prescribed and carry an epinephrine auto-injector, and be advised which types of seafood to avoid. Usually people allergic to fish can eat shellfish but some caution is needed to avoid cross-contamination. Reading labels along with understanding how foods are prepared are important skills for managing your allergy. You’ll also need to consider other situations, such as dining out for business or pleasure, dating and travelling. 

As for other treatments, there is less experience with oral immunotherapy (OIT) in adults than in children and less experience with fish than some other foods. 


Learn more

Do you have a question you’d like to ask an allergist in the months to come? If so, send it along to us at info@foodallergycanada.ca. Please note: The allergists in this series answer questions on general topics, please talk to your doctor if you have questions about your own health or the health of your child.


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