A food allergy is an immune system reaction to a specific food, and requires the use of food challenges to determine if an allergy exists. Allergic sensitization is defined by the presence of specific IgE antibodies in the blood. Food allergy, defined as an adverse immune response to food proteins, affects as many as 6% of young children and 3% to 4% of adults.

A Congressional bill requiring food makers to list on their product labels any of the eight most common food allergens was passed in 2006. The measure would require plain English labeling if a product contains wheat, milk, soy, peanuts, tree nuts, fish, shellfish, or eggs. Those allergens account for an estimated 90 percent of all food allergies.

A food allergy is an allergic reaction to a particular food. A much more common condition, food intolerance, isn't an allergic reaction but is any other undesirable effect of eating a particular food. Many people can't tolerate certain foods for various reasons other than food allergy; for example, they may lack an enzyme necessary for digesting the food. If a person's digestive system can't tolerate certain foods, the result can be gastrointestinal distress, gas, nausea, diarrhea, or other problems. In general, allergic reactions aren't responsible for these symptoms.
   Wheat, milk, soy, peanuts, tree nuts, fish, shellfish, or eggs have allergens that account for an estimated 90 percent of all food allergies. Peanut allergy and milk allergy are common, so is wheat gluten allergy. Individuals taking medications that reduce acid secretion or neutralize the acidity within the stomach, may be setting up a situation where harmless food proteins may become potential allergens.
   Tree nuts, such as cashews and walnuts, can trigger serious food allergic reactions. However, children's allergies to cashews are more severe than peanut allergy.

Symptoms of Food Allergy
Food-induced allergic reactions are responsible for a variety of symptoms involving the skin, gastrointestinal tract, and respiratory tract and might be caused by IgE-mediated and non-IgE-mediated (cellular) mechanisms. Although any food can provoke a reaction, relatively few foods are responsible for the vast majority of significant food-induced allergic reactions: milk, egg, peanuts, tree nuts, fish, and shellfish.

Food Allergy Diagnosis
A systematic approach to diagnosis includes a careful history, followed by laboratory studies, elimination diets, and often food challenges to confirm a diagnosis.

Food Allergy and Asthma
The presence of a food allergy may increase asthma in children, according to a study in the May 2005 Journal of Allergy & Clinical Immunology. Julie Wang, MD, from Mount Sinai Hospital, New York, and colleagues evaluated blood serum samples from 504 children with asthma, ages 4-9 years old, randomly selected from the National Cooperative Inner City Asthma Study (NCICAS). They sought to determine the prevalence rate of food allergy among inner city children with asthma. Since the data was obtained randomly and anonymously, researchers were unable to determine if a food allergy existed in the children evaluated. Researchers found that the prevalence of food sensitization, and likely food allergy, is highly prevalent in inner city children with asthma. After testing the children for specific IgE to six common food allergens (egg, milk, soy, peanut, wheat and fish), researchers found:

- Forty-five percent of the children were sensitive to at least one food allergen.

- Children sensitive to food had higher rates of hospitalizations due to their asthma.

- Children sensitized to food required more steroid medications to manage their asthma symptoms.

- Children sensitized specifically to soy and fish had significantly higher rates of emergency department visits, hospitalizations and increased medication use.

While previous studies have shown a link between asthma and food allergy, the current JACI study is one of the first to demonstrate a correlation between food sensitization and the severity of asthma symptoms. Researchers concluded that the presence of food sensitization may serve as a marker for identifying children with more severe asthma. They recommend that caretakers should consider screening patients with moderate to severe asthma whose disease is not well controlled with standard asthma medications.

Food allergy symptom
Allergens in food are absorbed from the intestinal tract and enter the blood stream. When they reach the skin, allergens can induce hives or eczema, and when they reach the lungs, they can cause asthma or spasm of the bronchi. As the allergens travel through the blood vessels, they can cause lightheadedness, weakness, and anaphylaxis, which is a sudden drop in blood pressure. Anaphylactic reactions are severe even when they start off with mild symptoms, such as a tingling in the mouth and throat or discomfort in the abdomen. They can be fatal if not treated quickly.

Food allergy testing
Food Allergy testing is controversial. A number of laboratories have set up ELISA / EIA (Enzyme Immunoassays) panels to test the presence of IgG antibodies to food allergens. This is based on the findings that certain subclasses of IgG are associated with the in vitro degranulation of basophils and mast cells, the activation of the complement cascade, (both of which are important mechanisms in allergy and anaphylaxis) and the observation that high circulating serum concentrations of some IgG subtypes have been measured in certain atopic individuals.The premise behind this testing is that high circulating levels of IgG antibodies are correlated with clinical food allergy signs and symptoms. These tests, one might extrapolate, would help the physician pinpoint food allergies in their patients so that patients might avoid these foods and their associated signs and symptoms.
     Food allergy test panels have found an increasing popularity among physicians who are looking for a reliable method to help in the diagnosis of an otherwise difficult diagnostic problem. Up until now, the only methods for the detection of common food allergy included skin tests, elimination and challenge diets, or double blind placebo controlled oral food challenges. Skin tests, although fairly reliable for the detection of IgE to environmental allergens, are not well correlated with food allergy signs and symptoms. Placebo controlled food challenges and elimination/challenge diets are extremely time consuming for the patient and practitioner and elimination/challenge diets require a high degree of patient motivation and compliance.

Food Allergy, Babies, and Newborns
Exclusive breastfeeding (with no cow's milk formulas or any supplemental food) is indicated during the first six months of life because it has a preventive effect against the onset of allergic symptoms that extends far beyond the period of breastfeeding. The avoidance of cow's milk in the early months of life has been shown to be an effective means of preventing allergies. The main foods that pose a high food allergy risk include cow's milk, eggs, peanuts, tree nuts (such as hazelnuts, walnuts, cashews, almonds, chestnuts, macadamias and pistachios), fish and other seafood. Other foods – even staples such as fruits, vegetables, meats, soy and cereals – also have the potential to cause allergies if introduced too early.
     In order to reduce food allergy in children, foods should be introduced in babies one at a time in small amounts. After the first six months of breast milk, babies should not be given mixed foods unless it is clear they are not allergic to any of the components.

Food allergy and babies, children - a different study, a different recommendation
Contrary to conventional wisdom, putting off solid foods for the first few months of an infant's life may not lower the risk of childhood allergies and asthma. The World Health Organization (WHO), the American Academy of Pediatrics (AAP) and other groups recommend that parents delay introducing solid foods for 4 to 6 months to curb children's allergy risk. However, the new findings, question the effectiveness of this strategy. German researchers found that among the 2,000 children with 6-year follow-up, those who received no solid foods before 4 to 6 months of age did not have a lower risk of nasal allergies, asthma or sensitization to common food allergens. Pediatrics, January 2008.

Egg food allergy
Most children seem to outgrow allergies to eggs, but it may take some of them into their late teens.

Nut food allergy
Ten percent of children allergic to tree nuts such as almonds and pecans eventually outgrow their allergy, even those who have had severe reactions. A blood test looking at a tree nut antibody provides a good indicator of when or if a child has lost the allergy.

Seed food allergy
Reports of food allergy to sesame seeds appear to be on the rise, particularly in developed nations where sesame is used in everything from hamburger buns to body lotion. In a review of reports in the medical literature, investigators found that recognized cases of sesame allergy have climbed steadily in the past 50 years, with most reports coming from developed countries. In fact, the study found, research in Australia, Western Europe and Israel suggests sesame is among the more common sources of food allergies.

Food Allergy and Teenagers
A large number of teenagers with food allergies admit to not reading food labels or knowingly eating foods labeled "may contain" allergens. Many of them do not always carry self-injectable epinephrine -- the medication that is immediately needed in the case of a severe allergic reaction. A survey found among teens with food allergy, 75 percent were allergic to peanuts, 20 percent to milk, 75 percent were allergic to two or more foods, 82 percent had had a severe anaphylaxis reaction some time in their lifetime. Better education and emphasis on carrying the epinephrine should be tried by parents.

Food Allergy Research
Treatment of eosinophilic esophagitis with specific food elimination diet directed by a combination of skin prick and patch tests.
Ann Allergy Asthma Immunol. 2005 Oct;95(4):336-43. Related Articles, Links
Division of Allergy and Immunology, The Children's Hospital of Philadelphia, Pennsylvania 19104-4399,
Eosinophilic esophagitis (EE) is a recently described disorder identified in patients with symptoms suggestive of gastroesophageal reflux disease (GERD) but unresponsive to conventional reflux therapies. Therapies have included corticosteroids, elemental diet, and diet restriction. We report our experience with skin prick and atopy patch testing and food elimination diets in patients diagnosed as having EE. OBJECTIVE: To identify food antigens that cause EE and the characteristics of patients who respond to food elimination vs those who are unresponsive. METHODS: Patients diagnosed as having EE had restricted diets based on skin prick and atopy patch testing results. Additional biopsies were performed after 4 to 8 weeks of restricted diet. Demographics, atopic tendencies, and food antigens were identified retrospectively in our food allergy database. RESULTS: A total of 146 patients diagnosed as having EE were evaluated with skin prick and atopy patch testing. Thirty-nine patients had unequivocal demonstration of food causing EE, with normalization of biopsy results on elimination and reoccurrence on reintroduction. An additional 73 patients, for a total 112 (77%) of 146 patients, had resolution of their EE as demonstrated by biopsy results. Fifteen (10%) of 146 patients were nonresponders manifested by no significant reduction in esophageal eosinophils despite restricted diet based on skin prick and atopy patch testing. Egg, milk, and soy were identified most frequently with skin prick testing, whereas corn, soy, and wheat were identified most frequently with atopy patch testing. CONCLUSION: In more than 75% of patients with EE, both symptoms and esophageal inflammation can be significantly improved with dietary elimination of foods. Skin prick and atopy patch testing can help identify foods in most patients.

Food allergy therapy.
Immunol Allergy Clin North Am. 2004 Nov;24(4):705-25, viii.
Novel approaches to the treatment and prevention of IgE-mediated food allergy include anti-IgE, food allergy vaccines, herbal preparations, and probiotics. They bring real hope to the allergy patients for whom no specific therapy is available. These immunomodulatory therapies have to be evaluated carefully for potential side effects, such as overstimulation of T helper cell type 1 immune antibodies. Animal models of food allergy are invaluable in testing new therapies for food allergy.

Food Allergy questions
Q. I just read your page on food allergy and I am very curious about the comment below. I have always believed this and I was wondering what your reasoning was behind this. Also have you found an alternative to taking acid suppressors (proton pump inhibitors) for children with acid relfux disease.
     "Individuals taking medications that reduce acid secretion or neutralize the acidity within the stomach, may be setting up a situation where harmless food proteins may become potential allergens."
     My daughter has a TON of food allergies/intolerances and has been on Prilosec since 2 months of age she is currently 27 months and have tried to challenge her a few times by reducing the dose of Prilosec with no luck. Allergic to egg, intolerant to milk, soy, wheat, oats, turkey, squash, apple, pear, most veggies and all other legumes.
     A. I am not fully certain but it could be that low acid levels in the stomach may prevent full degradation of proteins and lead to reduced digestion. You may wish to ask your doctor who is prescribing the PPI.

Q. I’ve long been plagued by multiple food allergies / sensitivities and the multitude of health problems they create for me. Will your newsletter publish information on food allergies and resolving food allergies?
   A. As we come across more information on food allergy treatment, we will include these studies in the newsletter.