Food allergies are a growing public health concern, affecting millions of people worldwide. It is crucial to understand the nature of food allergies, their causes, symptoms, and management to ensure the safety and well-being of those affected. This article delves into the intricate relationship between food allergies and proteins, exploring the mechanisms behind allergic reactions, common allergens, diagnostic approaches, and strategies for prevention and treatment.
Understanding Food Allergies
A food allergy is an adverse immune response to a specific food protein. The body mistakenly identifies a food protein as harmful and triggers an immune reaction. According to the Centers for Disease Control and Prevention (CDC), food allergies affect approximately 6% of adults and 8% of children in the United States. Food allergies are the leading cause of anaphylaxis, a sudden, severe, and potentially life-threatening allergic reaction.
Food Allergy vs. Food Intolerance
It's essential to distinguish between food allergy and food intolerance. Food allergies involve the immune system, while food intolerances do not. Food intolerances are typically caused by enzyme deficiencies or sensitivities to food additives. Symptoms of food intolerance can mimic those of food allergies, such as diarrhea, nausea, and abdominal pain.
The Role of Proteins in Food Allergies
Food allergens are almost always proteins, but not all food proteins are allergens. A food allergen is a protein that can elicit an immunoglobulin E (IgE) response and, upon subsequent exposures, trigger a clinical reaction.
How Proteins Trigger Allergic Reactions
When a person with a food allergy consumes a food containing the allergenic protein, their immune system produces IgE antibodies. These antibodies attach to cells in the skin, lungs, and gastrointestinal (GI) tract. Upon subsequent exposure to the same allergen, these cells release chemicals, including histamine, causing allergic symptoms.
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Characteristics of Food Allergens
Despite increasing knowledge of the structure and amino acid sequences of identified allergens, only a few biochemical characteristics can be associated with food allergens. Food allergens must survive food processing, digestive enzymes, and interact with the immune system.
Common Food Allergens
While more than 160 foods can cause allergic reactions, a few major allergens account for most reactions. The Food Allergen Labeling and Consumer Protection Act (FALCPA) of 2004 identified eight major food allergens:
- Milk
- Eggs
- Fish (e.g., bass, flounder, cod)
- Crustacean shellfish (e.g., crab, lobster, shrimp)
- Tree nuts (e.g., almonds, walnuts, pecans)
- Peanuts
- Wheat
- Soybeans
The Food Allergy Safety, Treatment, Education and Research (FASTER) Act of 2021 declared sesame as the ninth major food allergen.
Cross-Reactivity
In some food groups, especially tree nuts and seafood, an allergy to one member of a food family may result in the person being allergic to other members of the same group. This is known as cross-reactivity.
Symptoms of Food Allergies
Symptoms of food allergies typically appear within minutes to two hours after consuming the offending food. Symptoms can range from mild to life-threatening and may include:
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- Hives or itchy rash
- Nausea or vomiting
- Stomach pain
- Diarrhea
- Cough, wheezing, or shortness of breath
- Swelling of the lips, throat, tongue, or eyelids
- Dizziness or faintness
- Drop in blood pressure
Anaphylaxis: A Severe Allergic Reaction
In some people, a food allergy can trigger anaphylaxis, a severe allergic reaction requiring emergency treatment. Symptoms of anaphylaxis may include difficulty breathing, dizziness, loss of consciousness, and a sudden drop in blood pressure.
Diagnosis of Food Allergies
Diagnosing food allergies involves a thorough medical history, physical examination, and allergy testing.
Allergy Testing
Allergy skin tests may determine which foods trigger allergic symptoms. In skin testing, a small amount of extract made from the food is placed on the back or arm. If a raised bump or small hive develops within 20 minutes, it indicates a possible allergy.
An IgE blood test may be recommended in certain cases, such as in patients with severe eczema.
Oral Food Challenge
Oral food challenges can confirm the diagnosis and are done by consuming the food in a medical setting to determine if it causes a reaction.
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Management and Treatment of Food Allergies
The best prevention for food allergies is strict avoidance of food allergens.
Reading Food Labels
Reading food labels is crucial to identify potential allergens in food products. The FALCPA requires that food labels clearly identify the food source names of any ingredients that are one of the major food allergens or contain protein derived from a major food allergen.
Emergency Treatment
People with food allergies should always carry epinephrine to be used in the event of an anaphylactic reaction. Epinephrine can be prescribed as an autoinjector or as a nasal spray.
Oral Immunotherapy
Oral immunotherapy is a newer treatment that involves desensitizing the immune system so that small amounts of a food can be tolerated as a safety measure in case of accidental exposure to a food allergen. Currently, peanuts are the only food for which an FDA-approved oral immunotherapy exists.
Specific Food Protein-Related Conditions
Food Protein-Induced Enterocolitis Syndrome (FPIES)
FPIES is a non-IgE-mediated food allergy that primarily affects infants and young children. Symptoms of FPIES typically involve the gastrointestinal system and can include vomiting, diarrhea, dehydration, and poor growth. Common triggers include cow's milk, soy, rice, and oats.
Alpha-Gal Syndrome (AGS)
AGS is a serious, potentially life-threatening allergic condition that can occur after the consumption of red meat and products made by mammals. Alpha-gal is a sugar molecule found in animal protein. Symptoms of AGS can include hives, nausea, vomiting, diarrhea, and difficulty breathing.
Protein Intolerance
Protein intolerance is a disorder that results from an adverse effect of the ingestion of food proteins. It develops through immunological, non-immunological, metabolic, genetic, and pharmacological mechanisms. It is often associated with gastrointestinal symptoms.
Food Allergies in Children
Food allergies are more common in children, especially toddlers and infants. Fortunately, children typically outgrow allergies to milk, soy, wheat, and eggs. However, peanut, tree nut, fish, and shellfish allergies tend to persist through adulthood.
Managing Food Allergies in Children
Managing food allergies in children requires careful planning and communication. Parents and caregivers should:
- Notify childcare providers, school personnel, and parents of the child's friends about the allergy.
- Explain food allergy symptoms and how to respond to an allergic reaction.
- Develop an action plan that describes how to care for the child during an allergic reaction.
- Ensure the child wears a medical alert bracelet or necklace.
Food Allergen Labeling and Regulations
The FALCPA and FASTER Act are laws that make it easier for consumers to identify allergens in food. The FDA enforces FALCPA in the labeling of foods the agency regulates, which include all foods except poultry, most meats, certain egg products, and most alcoholic beverages.
Cross-Contact
Cross-contact occurs when a residue or trace amount of an allergenic food becomes incorporated into another food not intended to contain it. Food allergen advisory statements, e.g., “may contain [allergen]” or “produced in a facility that also uses [allergen],” should not be used as a substitute for adhering to current good manufacturing practices and must be truthful and not misleading.