Food allergens are often found in common foods like milk, eggs, wheat, soybeans, peanuts, tree nuts, fish, shellfish, fruits, vegetables, spices, and other ingredients. Food additives can also cause allergic reactions. The most commonly known allergen is cow’s milk protein. Other examples include egg white, gluten from grains, sesame seeds, shrimp, crab, lobster, chocolate, tomatoes, citrus fruit, strawberries, kiwi, almonds, hazelnuts, pecans, walnut oil, mustard seed, corn syrup, sugar, yeast extract, sulfites, monosodium glutamate, artificial sweeteners, preservatives, flavorings, colorings, and salt. A person who eats something containing one of these substances will likely experience symptoms within minutes to hours after ingestion. These responses range from mild itching to severe life-threatening shock. In addition, many foods are associated with more than one type of allergic reaction.
The most common types of food-related reactions
These can range from mild discomfort to severe anaphylaxis. Symptoms include vomiting, diarrhea, abdominal pain, nausea, hives, itching, shortness of breath, wheezing, coughing, swelling of lips/tongue/throat, difficulty swallowing, fainting, dizziness, headache, blurred vision, weakness, numbness, tingling, confusion, seizures, loss of consciousness, coma, shock, cardiac arrest.
These can also be life-threatening. They involve inflammation of the airways leading to breathing difficulties, including asthma attacks, bronchospasm, rhinitis, sinusitis, nasal congestion, hoarseness, cough, sore throat, sneezing, itchy eyes, runny nose, watery eyes, tightness around the chest area, trouble sleeping, fatigue, muscle aches, joint pains, skin rashes, etc.
These may occur on any part of the body but usually appear on the face, hands, or feet. Skin symptoms can vary depending on which organ is affected by the allergen. Common examples include eczema, urticaria, and angioedema. Other systemic effects include other organs outside the digestive tract and blood vessels. Examples include fever, hypotension, rash, pruritus, flushing, palpitations, sweating, pallor, diaphoresis, facial edema, dyspnea, dysphagia, syncope, vertigo, malaise, myalgia, arthralgias, arthritis, lymphadenopathy, eosinophilia, leukocytosis, thrombocytopenia, hemolysis, hyperglycemia, hypoglycemia, lipoid nephrosis, proteinuria, and renal failure.
Food allergens come mainly from plants, animals, fungi, and bacterial sources. Some food allergens are found only in specific parts of plants; for example, peanuts contain no gluten, so those who have celiac disease cannot eat wheat products containing gluten without risk of developing intestinal damage. Food allergens often share structural similarities, making cross-reactivity possible between unrelated substances. Cross-reactivity occurs when antibodies produced against one substance recognize another similar molecule. Antibodies bind to these molecules causing their removal from circulation. However, this does not mean that the antibody will cause the same effect as the original antigen. It depends upon how much of each substance was consumed at different times during development. Genetics plays a role in determining whether someone develops a particular food allergy. People inherit genes from both parents. If either parent carries a gene mutation that causes an abnormal structure in its DNA sequence, then there is a chance that offspring carrying the mutated gene will express the abnormality. A person’s genetic makeup affects what kinds of foods he or she can tolerate because his or her own cells produce special receptors called T cell receptors that help identify foreign antigens.
Environmental factors play a role in triggering the onset of food allergies. Exposure to environmental triggers increases the likelihood that a child will develop a food allergy. Factors like family history, age, gender, diet, stress levels, infections, medications, genetics, environment, and lifestyle contribute to the development of food allergies. There are two main theories about why exposure to environmental factors leads to the development of food allergies. One theory suggests that early exposures lead to tolerance while later exposures result in sensitization. Another theory states that repeated exposure results in desensitization.
Food allergies should always be diagnosed by a physician. Diagnosing food allergies requires careful observation of the patient’s response to various foods. Testing for IgE mediated hypersensitivity is recommended if the diagnosis remains uncertain after observing clinical manifestations following ingestion of suspected offending agents.
There is currently no cure for food allergies. Treatment focuses on reducing the severity of symptoms and preventing future episodes.
People with food allergies must avoid certain foods due to potential reactions. They also need to take precautions to prevent accidental consumption of potentially dangerous items. Anaphylactic shock can happen within minutes of eating something that contains a known allergen. Symptoms include hives, itching, wheezing, shortness of breath, chest tightness, nausea, vomiting, diarrhea, fainting, confusion, seizures, and loss of consciousness.