Introduction:
Food allergies affect many people globally, with an estimated prevalence of around four percent in children and one percent in adults. These numbers have been increasing over the past twenty years, drawing attention to the seriousness of the issue. However, the reported prevalence rates can vary due to the complex nature of food allergies. Some adverse reactions to food may resemble allergies but are not allergic. It is commonly believed that about 25 percent of adults in the Western world have food allergies. However, when proper diagnosis methods such as testing and oral food challenge (OFC) are used, the true prevalence rates are lower. The rates are closer to eight percent in young children and less than 4 percent in adults. This highlights the need for accurate assessment and understanding of food allergies to ensure appropriate management and support for those affected.
How Does Food Allergy Differ From Food Intolerance?
Most of the time, when people report reactions to food, they are experiencing food intolerances, not food allergies. Food intolerances occur when our bodies have trouble digesting or processing certain foods. They are not related to our immune system. They can have various causes, like the presence of toxins or pathogens in the food, the presence of certain substances like caffeine or alcohol, or our bodies lacking certain enzymes needed for digestion.
Whereas food allergies involve the immune system. They arise when the immune system mistakenly recognizes proteins in food as harmful and initiates an immune response against them. Food allergies can lead to a wide range of symptoms affecting different body parts, including the skin, respiratory system, or cardiovascular system. In addition, food allergies are not a single condition but a spectrum of various disorders.
Diagnosing food allergies can be challenging because the tests available, like the skin prick or specific IgE test, have limitations. They may show cross-reactivity or cannot accurately predict the severity of an allergic reaction. Considering the clinical symptoms alongside the test results is essential to make an accurate diagnosis.
Food intolerances are distinct from food allergies as they do not trigger an immune system response. They occur due to various factors, such as the characteristics of the food itself, contamination, or specific issues within individuals. The symptoms of food intolerance are typically linked to the quantity of food consumed and may not consistently occur. Examples of food intolerances include lactose intolerance and specific metabolic disorders.
What Are the Types of Food Allergies?
Food allergies are categorized into three types based on the underlying immunological mechanism involved.
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IgE-mediated food allergy.
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Non-IgE food allergy.
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Mixed IgE-cell-mediated food allergy.
IgE-Mediated Food Allergy:
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Most common type in the Western world, especially in children under three years of age.
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Immediate, reproducible allergic reactions caused by food-specific IgE antibodies.
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Symptoms include hives, angioedema, low blood pressure, bronchospasm, and gastrointestinal issues.
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Can lead to anaphylaxis, a severe and potentially life-threatening reaction.
Non-IgE Food Allergy:
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Immunologic reactions to food without detectable food-specific IgE antibodies.
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Includes conditions like eosinophilic esophagitis, food protein-induced enterocolitis, and food protein-induced allergic proctocolitis.
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Manifests as gastrointestinal disorders, often with slow onset and symptoms similar to common conditions like colic and reflux.
Mixed IgE-Cell-Mediated Food Allergy:
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Involves both IgE antibodies and immune cells in the allergic reaction.
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Conditions like eosinophilic gastroenteritis and atopic dermatitis fall under this category.
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Symptoms can affect the gastrointestinal tract and skin, varying in severity and response to food-avoidance diets.
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Additionally, there is a pollen-associated type of food allergy known as the pollen food syndrome or oral allergy syndrome, where certain pollens and fruits/vegetables share allergenic epitopes, leading to allergic reactions primarily in the mouth and throat.
Sensitivity to food chemicals, such as amines, salicylates, and artificial additives, can cause adverse reactions similar to allergies but is not immune-mediated. IgE-mediated food allergy is characterized by the development of specific IgE antibodies against food allergens, leading to immediate allergic reactions upon exposure to those foods.
How Is Food Allergy in Children Diagnosed?
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A thorough history is crucial for diagnosing food allergies, and the healthcare professional will take an allergy-focused clinical history.
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The doctor will take the personal and family history of atopy.
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The first allergy consultation will last for at least 30 minutes.
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The skin prick test (SPT) is commonly used to investigate food allergies, especially in children and adults.
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SPT involves pricking the skin with allergen extracts and measuring the wheal or erythema response.
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SPT results should be interpreted in the context of the patient's clinical history and do not necessarily indicate a clinical allergy.
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Allergen-specific IgE tests, such as the RAST (Radioallergosorbent) test, measure specific IgE in the serum and are an alternative to SPT.
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Component-resolved diagnostics (CRD) can provide specific information about allergenicity and help develop individualized action plans.
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Basophil activation tests (BAT) detect and measure basophil degranulation as an allergy marker.
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Oral food challenges (OFC) are considered the gold standard for diagnosing food allergies and involve gradually administering the suspected allergen.
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High-risk challenges should be conducted in a safe environment with resuscitation facilities.
How Is Food Allergy in Children Managed?
Treatment of food allergy primarily involves counseling to avoid the offending food. This includes reading food labels, taking precautions when dining out, and being mindful of language barriers when traveling. A written allergy action plan is also beneficial for allergic children, which includes information on detecting allergic reactions and using rescue medications. Oral immunotherapy (OIT) is being researched for peanut, cow's milk, and egg allergies, but formal protocols still need to be developed in most countries. Palforzia is a Food and Drug Administration-approved medication for peanut allergy, but it has limitations and does not provide a permanent cure. OIT duration can extend over months or years. Adjuvants like probiotics and biologicals like Omalizumab are being studied to enhance tolerance and reduce side effects. Baked food, which is less allergenic, may help induce natural tolerance in children with milk and egg allergies. The early introduction of allergenic foods, such as peanuts, eggs, and cow's milk, has been shown to prevent allergies in some studies.
Conclusion:
Food allergies are an increasingly prevalent issue, particularly among children below three years of age. Sensitization can occur either directly or through breastfeeding, leading to the development of multiple allergies. It is common for cross-reactivity to happen, such as between peanuts and tree nuts or cow's milk and goat's milk. Major allergens include cow's milk, eggs, peanuts, tree nuts, wheat, soy, fish, shellfish, crustaceans, and cephalopods. Diagnosis involves a thorough assessment of medical history, physical examination, and relevant tests, while elimination diets help identify specific allergens. While some children may outgrow their allergies, those related to peanuts, tree nuts, fish, shellfish, crustaceans, and cephalopods persist throughout life. Managing food allergies entails avoiding allergenic foods and being prepared to address any allergic reactions that may occur.
