Allergies occur when the immune system reacts to typically harmless environmental substances, known as allergens, such as pollen, dust mites, pet dander, or certain foods and medications. While many people develop allergies in childhood, new allergic reactions can appear later in life, even to previously tolerated substances. These reactions result from specific changes within the body’s immune response.
Why Allergies Can Appear Unexpectedly
The immune system is a dynamic network that can develop new sensitivities over time. When it mistakenly identifies a harmless substance as a threat, it produces antibodies. This process, called sensitization, can occur without immediate symptoms, making later allergic reactions seem sudden. Subsequent exposure to the allergen then triggers noticeable symptoms. Symptoms of a new allergy can vary significantly in their presentation and severity, ranging from mild itching or sneezing to more severe responses. An allergy is a specific immune response where the body overreacts to a foreign substance, and this response can be initiated or altered by new exposures or shifts in the body’s overall sensitivity.
Factors Contributing to New Allergic Reactions
Allergies can develop at any age due to factors including changes in immune function or new sensitizations. Nearly half of adults who experience food allergies report first noticing symptoms in adulthood. The immune system can become more sensitive to previously tolerated allergens as people age.
New Environments and Exposures
Moving to a new environment or new exposures can trigger new allergies. For instance, encountering different types of plants or higher concentrations of pollen, getting a new pet, or changing dietary habits can lead to sensitivity. Even common substances like dust mites or specific medications can become new triggers.
Cross-Reactivity
Cross-reactivity is another mechanism where the immune system confuses similar proteins found in different substances. This can lead to reactions to items not directly allergic to, such as in pollen-food syndrome (also known as oral allergy syndrome). For example, someone with a birch pollen allergy might experience symptoms when eating raw apples or carrots because their proteins are structurally similar to birch pollen proteins. This occurs when pollen-specific antibodies react with related proteins in certain fruits, vegetables, or nuts.
Environmental Factors
Environmental factors also play a role in new allergy development. Air pollution and climate change can cause plants to produce more pollen over longer seasons, intensifying allergen exposure. Reduced indoor ventilation can also increase exposure to indoor allergens.
Overall Health Changes
Changes in overall health can influence immune responses. Viral infections or periods of increased stress can temporarily alter immune function, and certain health conditions can contribute to new allergies.
Allergy Versus Other Sensitivities
Distinguishing a true allergic reaction from other sensitivities is important, as only allergies involve a specific immune system response. A food intolerance, for example, primarily affects the digestive system and results from the body’s inability to properly digest a food component, such as lactose. Symptoms involve gastrointestinal discomfort like bloating, stomach pain, or diarrhea, and are often dose-dependent. Unlike allergies, food intolerances do not involve the immune system and are not life-threatening.
Chemical sensitivities, such as reactions to fragrances or cleaning products, can cause symptoms like irritation, headaches, or respiratory discomfort. These reactions are generally not immune-mediated, distinguishing them from true allergies, and are often triggered by direct irritation.
Pharmacological reactions are adverse effects to medications that may mimic allergy symptoms but are not immune-mediated. These reactions are predictable based on the drug’s known properties and can include side effects like nausea or skin rashes.
When to Seek Medical Advice
If new or unexplained symptoms suggest an allergic reaction, seeking medical advice is important. Immediate medical attention is necessary for signs of anaphylaxis, a severe and potentially life-threatening allergic reaction. Symptoms of anaphylaxis can include difficulty breathing, swelling of the throat or tongue, hives, a sudden widespread rash, or a drop in blood pressure. These severe symptoms often appear rapidly after allergen exposure.
Consulting an allergist is advisable for diagnosis and management of new or persistent allergic symptoms. An allergist can conduct tests, such as skin prick or blood tests, to identify triggering allergens. Accurate diagnosis helps differentiate true allergies from other conditions.
A healthcare professional can recommend management strategies. These might include avoiding identified allergens, using antihistamines, or carrying an epinephrine auto-injector for severe reactions. An allergist can also discuss allergen immunotherapy for long-term management.