Focus - Health Tips » Food Allergies
By Dr. Moghissi - September 2006
A few years ago, guidelines were published in the Annals of Allergy, Asthma and Immunology to help clarify ways to diagnose and treat food allergies. A true food allergy is caused by antibodies called IgG, other adverse reactions to foods are called intolerances or sensitivities and occur by various other methods. The severe (and sometimes fatal) reaction to peanuts, for example, is a true food allergy.
About one quarter of people in the western world will have either an allergic reaction or intolerance to some type of food throughout their lifetime, but it is especially common in childhood. True food allergies are not common, and people with eczema, asthma or other allergies are most susceptible. Children who are allergic to one food are likely to develop allergies to multiple foods.
Allergies and sensitivities to most foods, such as milk, wheat and eggs often resolve before adulthood, but peanut, tree nut, and seafood allergies are more likely to be lifelong. Adults most commonly develop allergies to fruits and vegetables, and this may be due to their similarities with pollens.
Symptoms can range anywhere from mild stomach issues, to rashes, to anaphylaxis (throat closing leading to respiratory arrest) and death. Anaphylaxis and death in patients who are not highly allergic most commonly occurs when the offending food is eaten just before or after exercise.
The diagnosis of food allergies is definitely not an exact science. Keeping a food log, and noting a consistent reaction after every exposure is helpful. People who are “allergic” (those with eczema, asthma or environmental allergies) are more likely to have true food allergies. Skin testing can be helpful for peanut, milk, egg, tree nut, fish and shellfish allergies, but less so for other foods. Unfortunately, many people will react to skin testing even though they are not allergic to that specific food. A negative test is usually pretty reliable though.
Patch testing and hair analyses may one day be considered useful, but at this time it’s unclear how reliable they are. A food challenge may be helpful, but only if the suspected food does not give a life threatening reaction! There are new blood tests that have become available in the past couple of years that appear to be much more reliable than those we had previously, and probably should be be considered when trying to diagnose whether someone in allergic to a particular food. Blood tests are most useful if there are a limited number of foods in question, as each kind of food needs a separate blood test.
Treatment is really just avoidance of that particular food. When avoided for long periods, some people are able to tolerate the foods eventually. Immunotherapy (allergy shots) for food is still experimental, and there are no known medications to prevent allergic reactions to food. Injectable epinephrine (epi-pen) is the preferred treatment for anaphylaxis.
A second related article (published in the same journal), discussed food allergies in infants. This had more to do with the prevention of food allergies by careful introduction of solids and other foods. Studies have found that introducing solids early (before 4 months of age) greatly increases the risk of developing eczema. Feeding cow’s milk formula in the first few days of life has been associated with a cow’s milk allergy. Early introduction of cereals will increase the risk for grass triggered asthma.
By breastfeeding exclusively for 6 months, then carefully adding solid foods, the risk for asthma and eczema in later childhood is significantly lowered. Children with a family history of asthma, allergies or eczema are especially at risk, and it is important to delay introduction of certain foods even longer. In general, avoiding allergenic foods early in life is effective in decreasing the risk of allergic reactions later in life.
What then, are the allergenic foods? Since the most common allergies in adults in various countries are directly related to the most common foods consumed in those countries, it can vary. In our culture we worry most about cow’s milk, egg, peanut, tree nuts, fish and seafood. Wheat is also becoming a more common allergen.
Cooking some foods make them less allergenic. Well done beef, cooking or heat treating fruits and vegetables (especially Kiwi, which has become more of a problem in the past few years), roasting hazelnuts, cooking chicken and eggs and boiling or frying peanuts (rather than roasting them), make them less likely to cause allergic reactions. In contrast, cooking (or baking) wheat does not help. When introducing foods to infants and children, this should be kept in mind. In general, in high risk children the introduction of peanuts, tree nuts, fish and shellfish should be delayed until at least 3 years of age.
Fortunately, many children will outgrow their food allergies. As noted earlier, if the offending food is strictly eliminated from the diet, many children and even adults will eventually no longer be allergic to those foods.
Hopefully this overview will be helpful in shedding some light on the complicated issues of food allergies. Unfortunately, there is not much we can do for people who already have these allergies, but we should be able to help the next generation by being careful when introducing foods to our littlest ones.
Copyright 2017 Jasmine Moghissi, MD,PC.