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Living with Food Allergies

Answers to Questions You May Not Have Thought to Ask

by Scott H. Sicherer, MD

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If you have a fish allergy, it is possible to enjoy fishing by taking a few precautions.

How much food needs to be eaten to trigger a reaction?
The amount of food that can trigger a reaction depends on an individual’s sensitivity. It is not easily predicted by any simple tests. For some people, trace amounts that are not easily visible to the naked eye may cause symptoms, and for others, a meal-size amount of a food or more may be required to trigger a reac­tion. Your doctor may be able to assess your level of sensitivity based on your history or your response to a feeding test.

Can smelling a food cause an allergic reaction?
Yes, but this type of exposure is unlikely to cause anaphylaxis.

When can smelling a food cause an allergic reaction?
When the protein from the food is distributed into the air.

Under what circumstances would food proteins become airborne?
This most often occurs from heating, such as in cooking. For example, the steam from scrambling eggs or frying fish and the vapor from boiling or frothing milk can carry proteins into the air. Another way proteins can get into the air is when the food is in a powdery form and gets disturbed, for example, when preparing foods with wheat flour, powdered milk, or dried egg powder. Last, manipulations of a food might spread some proteins into the air nearby, for example, when peel­ing an orange or cracking peanuts.

Dr. Scott Sicherer

In what settings might there be an abundance of food proteins in the air?
Examples include occupational settings, such as a bakery or food-processing factory; markets where a high concen­tration of the food is being processed or heated, such as a seafood market; and food stands or kitchen locations where foods are being heated, such as roasting nuts, or frothing milk at a coffee shop.

Is smelling a food likely to cause an allergic reaction?
Rarely. Most smells from foods are due to organic compounds and no appreciable proteins. For example, the smell of peanut butter is not from any significant protein in the air. Odors from foods that are not being actively heated are unlikely to expel any appre­ciable allergenic proteins.

What kinds of symptoms might happen from airborne food proteins?
The symptoms would be similar to those from allergens such as pollen and animal dander. Namely, people may experience itchy eyes, sneezing, runny nose, and for people with asthma, a cough or wheeze.

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Although every allergen is in the store, you’re not likely to experience an allergic reaction merely from shopping.

Can touching a food cause an allergic reaction?
Yes, but anaphylaxis is unlikely.

What kinds of symptoms might happen from touching a food?
The most common skin symptoms are red blotches, hives, and itchiness. But touching the food does not usually cause symptoms. The skin barrier pre­vents the proteins from reaching the immune system. Younger children are often more susceptible to skin reactions from direct contact, especially if their skin barrier is compromised by eczema rashes. The eyes are also sensitive to allergens, so an allergen from the fingers rubbed into the eyes can result in sig­nificant redness and swelling. Can a severe reaction happen from touching or smelling a food?
Rarely. If a person with asthma breathes in a large inhalation of a food allergen, he or she might experience a significant asthma attack. If a large area of abraded skin is exposed to an allergen, there may be more absorption, leading to stronger reactions. However, these are unusual circumstances. The primary concern about casual exposure to a food is transferring the food from the fingers into the mouth.

What are some surprising mistakes that have led to allergic reactions?
Studies have shown that sometimes parents or other family members fed an allergen purposefully to a child with allergies, or allergic individuals pur­posefully ate foods they were allergic to, resulting in reactions. The reasons for this include curiosity, thinking a small amount would be OK, and testing to see if the allergy had resolved. If you are unsure you have an allergy, always dis­cuss this with your doctor before trying an allergen at home. Teach caretakers to do the same. Can a person with a tree nut allergy be near oak trees with acorns?
Acorns are tree nuts, and they might be allergens if eaten, but they are too sour to eat, so there is no literature about reactions from eating them. Like other nuts, it is not likely that touching them would result in any significant allergic reactions.

Can a person with a seafood allergy swim in the ocean?
Yes. I am not aware of any reports of a person being allergic to seawater based on an allergy to fish or shellfish. This is ably true for several reasons. The dilution of proteins in the ocean is tre­mendous. The concentration of allergenic proteins in the water becomes irrelevant. Second, the allergenic proteins in fish or shellfish are muscle proteins that would not be directly leaching into the water.

Can a person with a fish allergy own pet fish?
Yes, since the allergenic proteins are inside the fish and are not being eaten. However, the fish food is often made of fish and shellfish. If you are handling the food, minimize skin exposure by tapping the food into the water from a cap or container and washing your hands afterward. The main risk here might be rubbing the fish food on your hand into your eye, causing swelling.

Can a person with a fish allergy go fishing?
Yes, although handling the fish or handling parts of the fish after cleaning could irritate the skin because of local­ized allergic reactions. The main risk would be of skin or eye reactions, and possibly ingestion reactions if there is transfer to the mouth. It is possible to enjoy fishing by reducing direct handling of the fish, rinsing hands afterward, and wearing gloves when possible.

Can a person with a seafood allergy go to a dolphin show or swim with dolphins?
Dolphins themselves do not have aller­genic fish proteins because they are mammals, but they are fed fish and swim in an en­closed area where dilution is less than that seen in the ocean. There­fore, there is some risk that the fish proteins they ingest are in the pool water and may cause symp­toms for a person with a fish allergy. I have had patients develop hives from the water when splashed at shows.

Can a person with a food allergy swim in a pool with others who may have eaten the food?
When young children are snacking and swimming, there is some risk that they may share food, so supervision is needed. A better choice is not to eat while swim­ming. There is a risk of choking, as well! The small amount of residual allergens that might be in a mouth or on the body of a person who is swimming is unlikely to be relevant to the allergic swimmer because of the dilution effect of the pool. This risk might increase if people are constantly eating in the pool and spilling food and if the pool is small. However, in most situations, there should be no significant concern about reacting to re­sidual food proteins in a swimming pool.

Can a person be allergic to seawater, pool water, or any water?
Yes, but usually this is caused by the temperature of the water. There is a problem called cold urticaria, where swimming in cold water, or coming out of a pool and getting chilled, causes hives. This is a kind of physically in­duced reaction where, we believe, the allergy cells respond to the change in temperature. It is rare for this form of reaction to progress beyond the skin. Antihistamines are often used for treat­ment. There is another rare illness, called aquagenic urticaria, where water of any temperature on the skin causes hives, but the person can still drink water.

Can tiny shrimp (copepods) in drinking water cause an allergic reaction?
Get ready to become a little grossed out. Yes, there is a microscopic animal re­lated to shrimp that lives in freshwater and is allowed to remain in safe drink­ing water, especially from sources in geographic areas that have excellent natural water available for drinking. When sources of natural drinking water exceed government standards, the water is unfiltered, leaving these microscopic animals behind. No harmful effects have been related to these creatures. Presum­ably, if they have shellfish-relevant proteins, there is too little to trigger a reaction based on their small size and dilution effects of the otherwise safe and clean drinking water. Thus, they seem not to be a concern. If you are concerned, a home water filter could remove them.

If a cow, pig, or chicken is fed allergens, such as peanut or soy, can I be allergic to that animal’s meat?
This should not be a concern, because the animal’s meat proteins do not change based on its diet. It does not have these food proteins within its meat.

Can a person with a food allergy go shopping in a supermarket?
Although every allergen is in the store, it is not likely that allergic reactions would be elicited merely from shopping. Still, there are a few things to consider. Before seating an allergic toddler in a shopping cart, it is prudent to wipe the surfaces since it is likely that the child might suck on the handle bar or other surfaces. If a person has a shellfish al­lergy, it may be prudent to avoid the area where seafood is being steamed, as the seafood proteins may be forced into the air transiently.


Dr. Scott Sicherer is a professor of pediatrics and chief of the Division of Pediatric Allergy and Immunology at Mount Sinai School of Medicine in New York, NY. He is also a re­searcher in the Jaffe Food Allergy Institute at Mount Sinai.

Excerpted with permission from Food Allergies: A Complete Guide for Eating When Your Life Depends on It, by Scott H. Sicherer, MD, copyright © 2013 by Scott H. Sicherer, MD, published by the Johns Hopkins University Press.

This article was originally published in Coping® with Allergies & Asthma magazine, Spring/Summer 2013.