An allergy occurs when the body’s immune system mistakenly identifies a typically harmless substance, known as an allergen, as a threat. This defensive action involves the production of antibodies. The primary antibody responsible for allergic reactions is Immunoglobulin E (IgE). When exposed to an allergen, IgE antibodies bind to immune cells, triggering the release of chemicals like histamine that cause the physical symptoms of an allergic response.
The Possibility of Developing Allergies Later in Life
The answer to whether new allergies can develop later in life is yes, a phenomenon often called adult-onset allergy. Many people assume that if they did not have allergies as a child, they are immune for life, but the immune system remains dynamic and adaptable. It is possible to develop sensitivities to substances previously tolerated for years.
This shift can happen at any point during adolescence or adulthood, with many patients beginning to experience symptoms in their 20s or 30s. Because the immune system is constantly changing, lifelong stability of one’s allergic status is uncommon. Developing a new allergy involves sensitization, where the immune system begins to recognize a formerly tolerated substance as dangerous, initiating the IgE-mediated response.
Biological Triggers and Mechanisms Behind New Sensitization
The development of new allergies in adulthood is often linked to changes in environmental exposure or internal biological shifts. Moving to a new geographic area exposes the immune system to different regional pollens and molds, leading to sensitization. Similarly, acquiring a new pet or beginning a job with high exposure to specific dusts or chemicals introduces novel allergens that can provoke an immune response.
Sensitization occurs when the immune system encounters an allergen and begins producing allergen-specific IgE antibodies. Once these antibodies attach to immune cells, the person is sensitized, and subsequent exposure triggers the allergic reaction. Internal factors, such as hormonal fluctuations during pregnancy or menopause, can also alter immune function and tolerance, occasionally resulting in new sensitivities.
Illness or viral infections may also alter the immune system’s regulatory mechanisms, sometimes leading to a loss of tolerance to previously harmless substances. A specific mechanism known as Pollen Food Allergy Syndrome (PFAS) involves cross-reactivity. Here, the immune system, already sensitized to a pollen, reacts to similar proteins found in certain raw fruits or vegetables. For instance, a person allergic to birch tree pollen might react to an apple because the body mistakes the apple protein for the pollen protein.
Common Categories of Adult-Onset Allergies
Many types of allergies commonly emerge for the first time in adult populations, often surprising individuals who have safely consumed or been exposed to the substance for decades. Among food allergies, shellfish (such as shrimp and lobster) and tree nuts are frequently cited as common adult-onset examples. Nearly half of adults with food allergies report developing at least one of them later in life.
Environmental or inhalant allergies are also prevalent adult-onset diagnoses. New sensitivities to airborne substances like dust mites, pet dander, or specific seasonal pollens can develop even without moving to a new area. These often manifest as allergic rhinitis, causing symptoms like congestion and sneezing.
Occupational allergies form another distinct category, developing due to repeated, high-level exposure in the workplace. Examples include sensitivity to latex, often seen in healthcare workers, or reactions to specific chemicals, flours, or dusts in manufacturing or industrial settings. Certain medications, like antibiotics or pain relievers, can also prompt a new allergic reaction after years of safe use.
Diagnosis and Ongoing Management
If new symptoms suggesting an allergy appear, consulting a board-certified allergist is the first step for accurate diagnosis. The process typically involves a detailed medical history followed by specific testing to identify the trigger. Skin prick tests expose the skin to trace amounts of common allergens, while specific IgE blood tests measure the level of allergy antibodies in the blood.
It is important to differentiate true IgE-mediated allergies from food intolerances, such as lactose intolerance, which relate to digestive issues and lack the specific immune response. Management begins with allergen avoidance once the trigger is identified, which is the most effective way to prevent reactions. Symptom relief can be achieved with over-the-counter or prescription medications, including antihistamines and nasal corticosteroids.
For severe allergies, the allergist may prescribe an epinephrine auto-injector, a rescue medication for life-threatening reactions. Long-term treatment options, such as immunotherapy, are available for certain environmental and insect venom allergies. Delivered through shots or sublingual drops, immunotherapy works by slowly introducing increasing doses of the allergen to retrain the immune system to become less reactive over three to five years.