Food allergies are immune system reactions to specific food proteins. While often associated with childhood, they can emerge at any age, including adulthood. This challenges the traditional view of allergies as solely pediatric conditions.
The Reality of Adult-Onset Food Allergies
Individuals can develop new food allergies later in life. A 2019 survey indicated that nearly half of U.S. adults with food allergies acquired at least one during adulthood. This can be surprising, especially if they have consumed these foods without issue for years. The immune system is dynamic and can change over time, explaining why new sensitivities emerge.
Factors Contributing to New Allergies in Adults
Several factors can contribute to new food allergies in adulthood. Changes in the gut microbiota, the community of microorganisms residing in the digestive tract, can play a role. An imbalance in these gut bacteria, known as dysbiosis, can affect immune regulation and increase susceptibility to allergic sensitization.
Environmental exposures, such as shifts in diet or travel to new regions, may also influence the immune system’s response to foods. The immune system itself undergoes changes with age, known as immunosenescence. This can lead to altered immune function, including increased inflammation and changes in antibody production, potentially raising the risk of new allergies.
Cross-reactivity with existing allergies, like pollen-food syndrome, is a common pathway for adult-onset food allergies. Proteins in certain foods are structurally similar to pollen proteins, causing the immune system to react to both. Genetic predispositions may also manifest later in life, making some individuals more prone to allergies with age.
Identifying Common Adult Food Allergens
Certain foods are frequently linked to adult-onset allergies. Shellfish, including crustaceans like shrimp and crab, and mollusks such as clams and mussels, are common triggers. Peanuts and tree nuts (like almonds, walnuts, and cashews) are also frequently identified as new allergens in adults. Fish is another food that can lead to adult-onset reactions.
Beyond these, a significant number of adult-onset food allergies are attributed to fruits and vegetables, often linked to Oral Allergy Syndrome (OAS), also known as Pollen-Food Syndrome (PFS). This occurs when individuals with pollen allergies experience symptoms after eating certain raw fruits, vegetables, or nuts due to similar proteins. Common examples of foods involved in OAS include apples, carrots, celery, peaches, and melons, particularly for those with birch or ragweed pollen allergies. Cooking these foods can often denature the problematic proteins, making them tolerable.
Symptoms and Diagnosis in Adults
Symptoms of adult-onset food allergies can vary widely, ranging from mild to severe. Mild symptoms often include hives or itchy rashes on the skin, digestive issues such as nausea, vomiting, or abdominal pain, and oral itching or tingling in the mouth, lips, or throat. More severe reactions can involve difficulty breathing, wheezing, a tightening of the throat, or a sudden drop in blood pressure, which can indicate anaphylaxis. Anaphylaxis is a potentially life-threatening reaction that requires immediate medical attention.
A doctor will take a detailed medical history, inquiring about specific foods consumed and the timing and nature of symptoms. Diagnostic tests may include skin prick tests, where a small amount of allergen is applied to the skin to observe a reaction. Blood tests can also measure the level of immunoglobulin E (IgE) antibodies, associated with allergic responses. In some cases, an allergist might recommend an oral food challenge, where increasing amounts of the suspected food are consumed under close medical supervision to confirm the allergy.
Living with a New Adult Food Allergy
Managing a newly diagnosed food allergy in adulthood involves strategies to ensure safety and quality of life. Strict avoidance of the identified allergen is the primary approach to prevent reactions. This includes carefully reading food labels, as ingredients can change and hidden allergens may be present. Many food labels are required to clearly list common allergens such as milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat.
Preventing cross-contamination, especially when preparing food at home or dining out, is also important. For individuals at risk of severe reactions, carrying emergency medication, such as an epinephrine auto-injector, is advised if prescribed by a doctor. While no quick cure exists, desensitization therapies like oral immunotherapy (OIT) are being explored to build tolerance. Consulting with an allergist or a registered dietitian can provide personalized guidance for a safe eating plan and navigating daily life.