Allergies To Food
What are food allergies?
Food allergies are when exposure to a food, either through ingestion, contact, inhalation, or injection results in an adverse immune reaction. This reaction can cause varying symptoms ranging from mild discomfort to life-threatening.
There are different types of food allergies that manifest from biological differences and unique properties of different allergens.
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IgE-mediated food allergies (Type I Hypersensitivity Reactions): 3
This is the most common type of food allergy and the IgE antibody plays a major role in the immune response. A reaction usually occurs within seconds to one hour after exposure to a food allergen, and rarely, a late-phase reaction can develop four to six hours after the first sign of symptoms.
Mild or moderate allergic reactions to food can include the following symptoms:
- rash or hives
- runny or itchy nose
- itching or tingling of the mouth
- swelling of the lips, face
- abdominal pain, diarrhea, nausea, or vomiting
Symptoms that indicate a severe allergic reaction called anaphylaxis (seek immediate medical attention):
- difficulty breathing, tightening of the airways
- swelling of the tongue or throat
- shock with a severe drop in blood pressure
- rapid pulse
- dizziness, lightheadedness, or loss of consciousness
Oral Allergy Syndrome (OAS)4
Oral Allergy Syndrome is a type of IgE-mediated food allergy that results in mostly oral and perioral symptoms. These symptoms usually occur within seconds of exposure to the offending food and can last from minutes to hours, but are usually mild and transient. In rare cases, anaphylaxis can occur.
The common culprit of OAS is prior sensitization to pollen allergens. Fruits, vegetables, nuts, and spices that share similar proteins to these pollens trigger an allergic reaction through cross-reactivity when ingested. Since some of these proteins are heat-labile, you may notice cooking trigger foods prevents a reaction.
Common symptoms:
- Mouth, tongue, and throat itching
- Lip swelling
- Throat tightness
Rarer symptoms:
- Throat or tongue swelling
- Facial rash
- Nose, eye, or ear symptoms
- Systemic symptoms (nausea, vomiting, abdominal pain, upper respiratory obstruction)
- Anaphylaxis
Alpha-gal syndrome5
Alpha-gal syndrome is an IgE-mediated food allergy to red meat and other mammal products due to an allergy to a sugar molecule called alpha-gal. This allergy is most often caused by tick bites, especially those from the Lone Star tick, that transmit alpha-gal into the body, which the immune system detects and can become sensitized against.
Allergic reactions are typically delayed three to six hours after exposure because alpha-gal molecules in red meat have to go through the digestion process before they enter the bloodstream, which is where the immune response occurs.
The symptoms that result from alpha-gal syndrome are similar to a type I hypersensitivity food allergy, with the key difference being a delayed reaction.
Food-dependent exercise-induced anaphylaxis (FDEIA)6
Food-dependent exercise-induced anaphylaxis is a rare food allergy characterized by the onset of anaphylaxis from exercise performed during or shortly after food ingestion. People who are allergic to certain foods (such as wheat, celery, shellfish, grapes, and nuts) are at risk of FDEIA.
The main culprit of FDEIA is a leaky intestine that allows food allergens from the bowel into the bloodstream, which results in an allergic reaction. Exercise and other cofactors such as aspirin, alcohol intake, infections, stress, or female sex hormones/menstruation increase intestinal permeability and lead to the cascade of events that result in symptoms.
Non-IgE mediated food allergies: 7
Non-IgE-mediated food allergies are adverse reactions to food where immune cells are driving the allergic response while IgE is absent. In contrast to IgE-mediated food allergies, reactions are usually delayed after exposure to foods.
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Food protein-induced allergic proctocolitis (FPIAP)
Food protein-induced allergic proctocolitis is a mild food allergic disorder that typically results in bloody/mucus-streaked stools or mild diarrhea in babies less than 6 months old, but can also occur in older children. This appears to result from eosinophilic infiltration of the rectosigmoid mucosa causing localized inflammation in the distal colon.
FPIAP is most common in exclusively breastfed infants who are indirectly exposed to cow's milk, soy (and other foods) via food proteins in breast milk that comes from the mother’s diet. It can also result from direct ingestion of cow's milk or soy-based infant formula.
Avoidance of offending foods and a maternal exclusion diet should improve symptoms in 72h - 2 weeks' time.
Food protein-induced enteropathy (FPE)
Food protein-induced enteropathy is a food allergic disorder that typically develops in infants shortly after introduction to cow's milk or soy in the diet. Chronic diarrhea and malabsorption along with intermittent vomiting are common symptoms for infants with FPE, which can result in abnormal growth or development. This appears to result from structural damage to the mucosa of the small intestine from food-specific T cell infiltration. FPE resembles celiac disease (gluten-sensitive enteropathy), although tends to be less severe and transient.
FPE is most common in formula-fed infants who are directly exposed to cow's milk or soy food proteins in infant formula.
Avoidance of offending foods should improve symptoms after several weeks.
Food protein-induced enterocolitis syndrome (FPIES)
Food protein-induced enterocolitis syndrome is a food allergic disorder that mainly causes profuse and repetitive vomiting, but can also cause diarrhea. Repeated episodes of vomiting and diarrhea can lead to dehydration, shock (from losing blood in vomit/diarrhea), lack of energy, a pale appearance, or hypothermia. Additionally, abnormal growth or development can occur from malnutrition. This appears to result from the presence of food-specific T cells and systemic activation of the innate immune system and mast cells.
FPIES typically results in formula-fed infants who are directly exposed to cow's milk or soy food proteins in infant formula during the first weeks to months of life. In infants four to seven months old, FPIES can result from the ingestion of solid foods. Adult-onset FPIES can also occur and is most frequently triggered by seafood.
Avoidance of offending foods should improve symptoms after 24 hours but may take as long as 10 days.
Celiac Disease(8, 9)
Celiac disease is a food-allergic autoimmune disorder triggered by eating gluten that can result in various symptoms from person to person. Common symptoms are diarrhea, weight loss, constipation, abdominal pain, and malabsorption, which can snowball into a variety of other symptoms such as anemia, osteoporosis, and neurologic disorders.
Gluten is hard to break down completely by our digestive system. The gluten protein fragments that remain after digestion bind with the transglutaminase enzyme to form unique peptides. These peptides can be recognized as 'foreign' by the immune system and result in the production of antibodies. These antibodies can trigger the immune system to attack tissue transglutaminase, which leads to atrophy of the small intestinal villi, a vital player in nutrient absorption and gastrointestinal function.
Currently, the only treatment for celiac disease is a lifelong, strict gluten-free diet leading to improvement of symptoms, and preventing the occurrence of refractory celiac disease (symptom improvement unresponsive to a gluten-free diet).
Food Intolerance
Like food allergies, food intolerance involves adverse reactions to food; however, immunological mechanisms are not involved. Food intolerance is a nonimmunological reaction that takes effect by metabolic deficiencies (e.g., lactase or fructase deficiency), pharmacological intolerance (e.g., caffeine or tyramine in aged cheese, salicylates in mints), toxicity (e.g., bacteria or contaminants like histamine), or psychological disorders.10
Because food intolerance is not an allergy and is fundamentally different from food allergies, the full extent of the disease is not covered under Generation Allergy Free.
Mixed IgE/Non-IgE-mediated food allergies:
Eosinophilic Gastrointestinal Diseases (EGIDs): 11
Eosinophilic gastrointestinal diseases are allergic inflammatory conditions that affect the gastrointestinal tract and are characterized by eosinophil infiltration triggered by food or aeroallergen allergies.
These disorders present with symptoms that are related to the area of the gastrointestinal tract that is affected.
Eosinophilic Esophagitis (EoE)
Involves eosinophil infiltration of the esophagus, which is normally devoid of eosinophils. Chronic EoE, if left untreated, can develop into progressive esophageal scarring and dysfunction.
Symptoms: Vomiting, chest or epigastric pain, trouble swallowing, and respiratory obstruction.
Eosinophilic Gastritis
Involves eosinophil infiltration of the stomach.
Symptoms: Vomiting, nausea, stomach pain, anorexia, malnutrition.
Eosinophilic Colitis
Involves eosinophil infiltration of the large intestine.
Symptoms: Diarrhea, abdominal pain, weight loss, and anorexia.
Eosinophilic Gastroenteritis
Involves eosinophil infiltration of the esophagus, stomach, and intestines. There are three forms depending on the location of eosinophil infiltration; infiltration of the mucosal lining is the mucosal form, infiltration of the smooth muscle is muscularis form, and infiltration of the outside lining is the serosal form.
Mucosal form symptoms: Vomiting, abdominal pain, diarrhea, blood loss in stools, iron-deficiency anemia, malabsorption, loss of proteins from the digestive tract, and failure to thrive (abnormal growth and development).
Muscularis form symptoms: Gastrointestinal obstruction, which can lead to vomiting, constipation, or abdominal pain.
Serosal form symptoms: Gastrointestinal swelling with higher peripheral eosinophil counts.