Q: On TV, a doctor said the “main theory” of why people develop shellfish allergy in adulthood relates to use of alcohol or antacids. She said these “affect the acidity in the stomach” and the way a person breaks down the now-allergenic food. I’ve never heard this. Is that the prevailing view?
Dr. Sicherer: I do not think this is a prevailing view, but the theory does deserve some attention. The theory surrounding antacids has to do with there being less digestion of the food, allowing more whole proteins to be seen by the immune system, or that some effect of the medication alters immune responses. This has been demonstrated in experiments using mice.
Studies have looked at antacid use in humans as a risk factor in developing food allergy, but without clear conclusions. When there has been an association, it could be that people with food allergy have more stomach issues leading them to use more antacids, making it look like the antacids caused food allergy when actually the antacids were being used more because of symptoms related to food allergy.
I am not aware of human studies showing that alcohol is associated with developing shellfish allergy. However, alcohol is often a food allergy co-factor, meaning it can lower the threshold of reactivity to a food, as can illness, exercise, or using aspirin-type medications. This could result in having symptoms when eating the food with alcohol, but not when eating it without the alcohol. Or, it could simply make reactions worse.
Antacids, Alcohol as Co-Factors
There is limited evidence that antacids may be a co-factor as well. Studies would be needed to see if these exposures are related to the development of food allergy.
In fact, there are many theories of how allergy can develop. Considerations include the route of exposure (air, skin, mouth), the amount ingested and frequency of consuming a food. Prevailing theories have been focusing on the idea that eating the food helps to generate normal immune responses, while exposures without eating (such as through skin with eczema) may lead in some people to allergic responses.
Pollens Can Hype Immune Response
The foods that seem to be more often associated with new onset adult food allergy are raw fruits and vegetables because of pollen-related food allergy, or allergy to shellfish, fish and tree nuts. The later onset of pollen-related allergies is likely attributable to having lived through multiple pollen seasons, hyping up the immune response to those proteins. This is an example of becoming allergic through protein in the air.
It is probably important that the most common adult-onset food allergies, shellfish and tree nuts, involve foods that are usually eaten intermittently as opposed to regularly.
Other aspects that are being considered with later onset allergies include hereditary risks, general nutrition, the person’s state of health and the types of germs in our bodies (our microbiome).
Dr. Scott Sicherer is a practicing allergist, clinical researcher and professor of pediatrics. He is Director of the Jaffe Food Allergy Institute and Chief of Pediatric Allergy and Immunology at the Icahn School of Medicine at Mount Sinai in New York. He’s also the author of Food Allergies: A Complete Guide for Eating When Your Life Depends On It.Submit a Question View all posts by this medical expert.