What is Food Allergy?
Having a food allergy means that the body has produced an unnatural overreaction in the immune system to a food protein. The allergic response is a very brisk one, and the body can react to even minute quantities of an offending food.
What are the Symptoms of a Food Allergy?
An allergic person’s body, upon exposure to the specific food, releases allergic chemicals that creates food allergy symptoms, such as vomiting, diarrhea, hives, and wheezing. Since the immune system is present throughout the body, many different parts of the body can be affected. Symptoms can be mild, such as a few hives in an area where the skin has briefly touched a food allergen, or it can be as severe as anaphylactic shock. A systemic allergic reaction is called anaphylaxis, which can be mild to severe, as well. It is essential to remember that the amount of allergen physically ingested does not predict how severe a food allergy will be, since even slight amounts can cause severe reactions.
- Symptoms of Food Allergy:
- Skin - Itching, Red Hot Flushing, Hives, Swelling
- Head/Neck - Eye Itching and Swelling, Nasal Sneezing and Congestion, Runny Eyes and Nose, Throat Itching and Swelling, Tongue Swelling, Voice Change and Cough
- Respiratory - Cough, Shortness of Breath, Wheezing, Bronchospasm
- Gastrointestinal - Stomach Pain, Nausea, Vomiting, Diarrhea
- Psychological - Anxiety, Inconsolable Crying, Feeling of Doom, Dizziness/Faintness
- Cardiovascular - Palpitations, Blood Pressure Changes, Shock
Dr. Siri and her staff at Midwest Food Allergy Center for Treatment (MFACT) can help you identify the symptoms accurately, develop an action plan, and provide appropriate education so that you can confidently treat and prevent severe food allergy attacks.
What Foods Can A Person Be Allergic To?
A person can be allergic to any food protein. However, the most common food allergies are to Peanuts, Tree Nuts, Egg, Fish, Shellfish, Milk, Soy, Wheat, and Corn. Allergies to these nine foods represent over 95% of food allergies in the United States. An allergy to meat used to be quite rare, but has growing been growing as of recent. A good resource for an overview of different allergenic foods is the American College of Allergy Asthma and Immunology.
- Common Food Allergies:
- Cow’s Milk
- Hen’s Egg
- Peanut (sometimes cross-reactive with other legumes)
- Tree Nuts (examples, Cashew, Walnut, Pistachio, Pecans, Hazelnut, Brazil Nut)
- Fish (examples, Cod Fish, Salmon, Mackerel)
- Shellfish (examples, Shrimp, Lobster, Crab, Scallops, Oysters, Clams)
- Seeds (examples, Sesame, Mustard)
What Part of the Body is Responsible for Food Allergies?
Special proteins that make up our immune system are intended to fight off foreign invaders to protect the body from harmful substances, such as parasites, viruses, and bacteria. The allergic person’s body has an abnormally set-up defense system to protect against things in the environment, like food proteins, which normally do not cause a body any harm. The abnormal defense mechanism is primarily due to allergen-specific antibodies, called Immunoglobulin E (IgE). IgE is activated when it recognizes the presence of its allergen, causing a special cell in the body called the Mast Cell, to release a cascade of chemicals, including histamine, prostaglandins, leukotrienes, chymase and tryptase.
- Food Allergy is Caused by Abnormal and Overproduction of Food-Specific Immunoglobulin E (IgE).
How Quickly Can a Reaction Be Seen After a Food Allergen is Ingested?
Symptoms of a food allergy may develop within minutes of being exposed to the food protein. For example, a peanut-allergic person may have immediate hives after touching peanut butter or they may notice their lips/mouth tingling and itching after eating a cookie that has been cross-contaminated with peanut. Depending on other factors, such as a person taking a medication like an antihistamine or having slow digestion due to eating a large fatty meal, a person may have symptoms of food allergy be variable or even delayed by several hours.
- Symptoms of a food allergy may develop within minutes of exposure.
How Does A Person Become Allergic?
The process of becoming allergic is called sensitization. There are three important factors to developing sensitization. These are Predisposition (inherited through your genes), Conditions and Timing, and Exposure. A person becomes sensitized after being exposed to the food protein, which may be through the airway, skin, mouth or gut, during a time when the body is susceptible.
The susceptibility to having allergies is called Atopy, which often is inherited. Although the tendency to have an allergy is inherited through our genes, specific allergies are not. This means that a parent who has allergic rhinitis and seasonal allergies may have one child who develops eczema and food allergy and another who has asthma. Even if you have severe allergies to shellfish, your child won’t necessarily have the same allergy, no different than your sibling who perhaps has no food allergies but has an allergy to bee stings.
Conditions and Timing
A person can develop an allergy at any time in her/his life to just about any protein. Food proteins that are highly allergenic are those that remain less digested after passing the stomach. The type of food, the way the food is prepared, and the amount of stomach acid present in the stomach all affect how the food protein looks when it encounters the digestive tract. It is known that roasting peanuts, for example, instead of boiling peanuts, creates more sturdy peanut proteins that aren’t broken down by natural stomach acids as easily. Bacteria in the gut, the use of antibiotics that affect gut health, having concurrent illnesses, hormones, age, gender, body fat percentage, and food additives are just some factors that can influence the sensitization process. Young people, especially pre-puberty, have very active immune systems as their bodies are encounter new allergens constantly, which makes this a prime time not only for developing tolerance to the environment and food, but also in developing allergies.
An individual cannot be allergic to a substance unless the individual has been exposed to the allergen before and developed sensitization (even once is enough). The exposure for allergic babies is still unclear it sensitization may have occurred during gestation, breast feeding, or even shortly after birth. The quantity and routes of exposure are also important. Even people who are not atopic can develop allergy with overwhelming allergen exposure in the right conditions, such as when the body is oversaturated. This has been seen in athletes who develop milk allergy after excess consumption of concentrated whey (a milk protein) powder. Skin health is a huge factor in allergy development. In all people (especially infants), soap, harsh chemicals, and residues on the skin cause a weakened barrier which in turn leads to dry skin and eczema. Untreated inflamed skin, areas of even mild eczema, is a prime source of sensitization to allergens, including food allergens. Since the skin is the largest organ of the body, it behooves all allergy sufferers to health and maintain the skin as best as possible.
- Factors That Contribute to Developing Food Allergies:
- Genetic Predisposition
- Conditions and Timing
How Do I Prevent Developing Food Allergies in Myself or My Child?
The keys to allergy prevention are multifold. As stated above, a healthy skin barrier is essential since our bodies contact so many allergens through the skin. Unnecessary antibiotics, additives, preservatives, harsh cleansers, and pesticides serve to suppress healthy bacteria on our skin and gut, which are symbiotic to our bodies. This includes small things we don’t think about such as antimicrobials in hand-sanitizers, personal care products, and baby wipes that also leave residues on our skin. Restoring natural bacteria may be helpful, as shown in some studies, with pre- and probiotics along with a healthful diet. Breastfeeding your infants and avoiding overeating or “overexposure” just make sense. Regarding the timing of food introduction, it was previously advised by national organizations to delay the introduction of allergenic foods into the diet of babies in hopes of preventing food allergy. The information on early food introduction has been transformed by recent clinical trials which support early introduction to peanut and possibly egg at 4 to 6 months of age. (LEAP - Learning Early about Peanut Allergy, LEAP-On - Persistence of Tolerance to Peanut, and EAT - Enquiring About Tolerance studies). Some foods introduced early did not show a benefit in reducing allergies, but more studies and information on prevention are underway.
Dr. Siri and her expert team at MFACT can delve into detail regarding the most up-to-date studies on food allergy and preventative measures, as well as on information regarding complementary treatments that may be helpful.
What is the difference between a Food Allergy and a Food Intolerance?
When Board-Certified Allergists and Immunologist think about the word “allergy,” whether it is a food allergy or another type of allergy, we think of an exquisitely hyperreactive condition, in which the chemical mediator IGE is present and overproduced, even when exposed to small quantities of the allergen. Having an allergy, especially if it is to a food, drug, stinging insect, or having allergic asthma, means that the condition may be life-threatening if allowed to go on unchecked. When someone uses the word “hyperreactivity” or “sensitized” this is essentially saying that someone has allergies to the offending agent. Although lay people may use the terms allergy, hyperreactivity or sensitization, these conditions usually connote the presence of IGE. There are some types of severe food allergies that invoke other cellular immune mechanisms that may not involve IGE but none-the-less have an immune basis. The types of food allergies listed in Table 1.
- Types of Food Allergies:
- Food allergy and Food anaphylaxis - IgE Mediated
- Food Pollen Syndrome or Oral Allergy Syndrome (OAS)
- Exercised-induced anaphylaxis, Food-Dependent
- Food Protein Induced Enterocolitis (FPIES)
- Adult Onset Food Protein Induced Enterocolitis
- Heiner Syndrome or Milk-Induced Pulmonary Disease / Pulmonary Hemosiderosis
- Delayed Anaphylaxis and/or Urticaria Caused by Meat
- Atopic Dermatitis, Food-Dependent
- Eosinophilic Esophagitis
- Eosinophilic Gastrointestinal Disorders
Celiac disease deserves a special notation. Celiac disease is an autoimmune inflammatory disease of the gut and may cause additional symptoms outside the gut (such as fatigue and skin rash), due to the ingestion of gluten. Gluten is present in common grains such as wheat, barley, and rye. The presence of gluten induces an immunological response that causes the body to attack the small intestinal cells, leading to abdominal pain, malabsorption of nutrients, anemia, and other symptoms. Long-term, a high risk for developing gut cancer, osteoporosis, and other health conditions exist for the untreated. Celiac disease can be diagnosed by blood tests, an endoscopy with biopsy, and response to a strict gluten free diet. A solid resource for more information is the website for the Celiac Disease Foundation at www.celiac.org.
- Celiac Disease is an Autoimmune Disease of the Gut Induced by the Presence of Gluten.
Having a food intolerance or a food sensitivity is a broader term for non-allergic problems with food. The common theme is that people with a food intolerance have some trouble with the digestion of one or more foods. These may include those with lactose-intolerance, fructose-intolerance, maltose- or isomaltose-intolerance, irritable bowel disease, food-induced interstitial cystitis, pseudo-allergic food reactions (scrombroid poisoning), and malabsorption syndromes (such as from infectious agents, after broad-spectrum antibiotic use, or overuse of artificial sweeteners). Some food issues may stem from other underlying health conditions, such as acid reflux (GERD or gastroesophageal reflux disease), atrophic gastritis, watermelon stomach, gall bladder and pancreas problems, inflammatory bowel disease, gastroenteritis, tropical sprue, mast cell disorders, abdominal migraines, endometriosis and other diseases. Symptoms often include nausea, gas, bloating, abdominal pain, and diarrhea. Due to the multitude of conditions that may be the culprit, a multidisciplinary and progressive approach is needed. Choosing Dr. Siri and her expert MFACT team means that they will take a comprehensive history and examination in order to “deep dive” into your health concerns to get to the bottom of the problem. We work with your Gastroenterologist and Primary Care Physician to point you into the right direction in order to find solutions.
How are Food Allergies Diagnosed?
After a complete health questionnaire and physical examination, MFACT’s Advanced Providers will perform diagnostic testing. We will look into the whole picture for allergies and specifically focus on food allergy concerns with both needle-free skin prick tests and blood tests to foods. IGE-mediated food allergy testing takes advantage of the presence of IGE in the skin or the blood for these tests. Both skin tests and blood tests are utilized for diagnosis since both tests are subject to interpretation and can have false positives as well as false negatives. Dr. Siri and her staff have a large and comprehensive food panel for skin prick tests and choose targeting testing to look for the presence of IGE sensitization. Our Advanced Providers are skilled at utilizing Food Component Blood Tests in order to predict allergy severity and tolerability. Testing to colorings and common additives is also available. Chemical patch testing may also be indicated if a skin rash exists to look for non-IGE mediated hypersensitivities. Additional blood tests may be indicated depending on the clinical picture. The gold standard for diagnosis is ultimately an in-office Oral Food Challenge, which is performed by MFACT’s skilled and experienced staff safely and effectively in patients who have ambiguous results or who may be outgrowing her/his food allergies.
Do Alternative Tests, Including Blood Tests, Help in the Diagnosis of Food Allergies?
There are various blood tests available through small private labs that employ different methods to assist the private pay patient in diagnosing food intolerances. These tests include leukocyte activity testing, leukocyte histamine release, cytotoxic assays, measurement of IGG/IGG4 and IGA to foods, and others, which at some point in time were promoted to be able to diagnose food allergy. Since reliability, repeatability, clinical trials or consistent relationship to symptoms or improvement could be proven, all these methods were labeled as unscientific, unproven, and not medically necessary. These tests are now being marketed to diagnose food intolerances rather than true food allergy. As reviewed above, since food intolerance can stem from so many different disorders, in MFACT’s opinion, it is hard to imagine that a single type of test could help the majority of people with food intolerance, although it may help some people by chance. IGG4 has been utilized in multitudes of proven research where elevated levels of IGG4 to specific foods indicate the effectiveness of food tolerance, desensitization, and immunotherapy. MFACT does not feel that IGG, IGG4 or IGA have utility in the diagnosis of food allergy, particularly since histamine-release is not triggered by these antibodies. Applied kinesiology is also a test that has been employed to diagnose food allergy and food intolerance. The basis for the testing is evaluating muscle strength and reactivity when holding various glass vials containing different foods. The results depend on variation in the food’s energy potential as it flows through a specific person’s body. The Physician’s at MFACT do not believe in the accuracy or reliability of applied kinesiology in the diagnosis of any food condition due to MFACT’s opinion that the scientific basis of any reaction to a food cannot be transmitted through a glass barrier nor affect a muscle group on the opposite side of the body and indeed without having any local effect.
How prevalent are Food Allergies in Children?
According to the CDC, food allergy in children increased ~50% in just 4 years, between 1997 and 2011. In 2011, ~15 million people in the U.S. had food allergies. This number equates to 1 in 13 children or about 2 children in every classroom.
Two-thirds or more of children with a milk or egg allergy may be able to tolerate baked-in milk and baked-in egg food products.
How do doctors evaluate Food Allergy?
Doctors and researchers utilize the following to evaluate Food Allergy:
History of a Food Specific Reaction
History of other Allergic Conditions (Asthma, Allergy, Eczema, Etc.)
Family History of Allergic Conditions (Asthma, Allergy, Eczema, Etc.)
Skin Prick Testing to Food Extracts
Skin Prick Testing to Fresh Food
Food Specific IGE Blood Tests
Food Specific Component IGE Blood Tests
Food Specific Food-Pollen Cross Reactivity IGE Blood Tests
Food Specific IGG is only measured and relevant to show that a person is actively ingesting the food as an indication of tolerance.
There is no role for Food Specific IGA testing in the evaluation of food allergy.
Food Patch testing is no longer thought to be useful.
How to Interpret Peanut Component IGE Testing
-Peanut Component Testing differentiates the Total IGE to Peanut blood test and evaluates the specific peanut protein that a person is allergic to.
-This test is only able to be assayed if the Total IGE to Peanut is at a high enough level for detection.
-Thus false negatives can occur. Ara h1 Risk of systemic reaction is high
Ara h2 Risk of systemic reaction is high, *Most associated with anaphylaxis
Ara h3 Risk of systemic reaction is high
Ara h8 Risk of local reactions, such as mouth/lip/throat itching and swelling, Usually the reactions milder with lower risk for systemic reactions. Cross reactive with plant pollen (such as birch tree pollen).
Ara h9 Risk of local reactions. The systemic reaction risk is mild to moderate. Cross reactive with plant pollen (such as birch tree pollen and pitted fruits).
How To Interpret Egg Component IGE Testing
Egg allergen component tests can help you determine the likelihood of reaction to products baked with egg, such as muffins or cookies, as well as the likelihood of allergy Persistence. High levels of egg white IgE may predict the likelihood of sensitivity, but may not be solely predictive of reactions to baked egg or allergy duration.
Knowing which protein your patient is sensitized to can help you develop a management plan.
Gal d2 Susceptible to heat denaturation. Higher risk of reaction to uncooked egg. Lower risk of reaction to baked egg. Patient likely to outgrow egg allergy.
Gal d1 Resistant to heat denaturation. Higher risk of reaction to all forms of egg. Patient less like to outgrow egg allergy with high levels of sIGE to ovomucoid.