Individuals can develop new allergies at any point in their lives, even to substances previously tolerated. While this can feel sudden, it has a clear scientific basis within the body’s immune system. Understanding how these reactions occur can help demystify their onset.
The Immune System and Allergy Development
Allergies arise from an overreaction of the immune system to typically harmless substances, known as allergens. The process begins with an initial exposure, called sensitization, where the immune system mistakenly identifies a benign substance as a threat. During this phase, specialized immune cells produce specific antibodies called immunoglobulin E (IgE).
These IgE antibodies then attach to the surface of mast cells, which are immune cells found in various tissues throughout the body, particularly in areas like the airways, skin, and gastrointestinal tract. The first exposure usually does not cause symptoms.
Upon subsequent exposure to the same allergen, the IgE antibodies on the mast cell surfaces bind to the allergen, triggering the mast cells to release chemical mediators, including histamine. Histamine causes blood vessels to dilate, mucus to form, and tissues to swell, leading to the familiar symptoms of an allergic reaction.
Common Reasons for New Allergy Onset
New allergies can appear due to various factors influencing the immune system’s response. A common reason is a change in exposure to allergens. For instance, moving to a new geographic region can introduce individuals to different types of pollen or environmental allergens, potentially triggering a new sensitivity. Acquiring a new pet can also lead to developing a dander allergy due to increased exposure.
Age-related changes in the immune system also play a role; new sensitivities can emerge in adulthood, often in people’s 20s or 30s. The immune system’s responsiveness can shift over time, leading it to react to substances previously tolerated.
Cross-reactivity is another factor, where an existing allergy to one substance, like pollen, can lead to reactions to seemingly unrelated foods containing similar proteins. For example, someone with a birch pollen allergy might develop symptoms after eating raw apples or certain nuts.
Certain medical conditions, such as illnesses that compromise the immune system, or significant physical or emotional stress, can influence the development of new allergies. Genetic predisposition can increase susceptibility, meaning a person may have always had the underlying tendency, only for a specific trigger or prolonged exposure to finally initiate the reaction.
Recognizing New Allergic Reactions
Recognizing a new allergic reaction involves identifying a range of symptoms that can affect various parts of the body. Skin reactions are common and may include hives (raised, itchy red welts) or eczema (itchy, inflamed patches of skin). Generalized itching can also occur without a visible rash.
Respiratory symptoms often resemble those of a cold or asthma, featuring sneezing, a runny or stuffy nose, coughing, wheezing, and shortness of breath. The eyes may become itchy, watery, red, or swollen.
Digestive issues can also indicate an allergic reaction, particularly to foods. These symptoms might include nausea, vomiting, diarrhea, or abdominal pain and cramping. Swelling of the lips, tongue, or throat can accompany these reactions, and a tingling sensation in the mouth may be an initial sign of a food allergy.
In severe cases, an allergic reaction can progress to anaphylaxis, a life-threatening emergency. Signs of anaphylaxis include widespread hives, difficulty breathing due to throat swelling or airway constriction, a sudden drop in blood pressure leading to dizziness or fainting, and a rapid or weak pulse.
What to Do When a New Allergy Appears
If you suspect you have developed a new allergy, consulting a healthcare professional is a sensible first step. A doctor, particularly an allergist, can perform diagnostic tests such as skin prick tests or blood tests to identify the specific allergens causing your symptoms. Skin prick tests involve placing small amounts of suspected allergens on the skin and observing for a reaction, while blood tests measure the levels of IgE antibodies to specific allergens.
Once an allergy is diagnosed, identifying and avoiding the specific triggers is a primary management strategy. For instance, if a pet allergy is confirmed, limiting exposure to the animal or its dander can help reduce symptoms. For seasonal allergies, monitoring pollen counts and staying indoors when levels are high can be beneficial.
For mild to moderate reactions, over-the-counter medications like antihistamines can help manage symptoms by blocking histamine release. Nasal steroid sprays and eye drops are also available for localized relief of respiratory and ocular symptoms.
In cases of severe allergies, particularly those with a risk of anaphylaxis, healthcare providers will likely prescribe an epinephrine auto-injector. It is important to carry this device at all times and know how to use it, as it can quickly counteract a severe allergic reaction. Even after using an auto-injector, emergency medical attention is necessary. For long-term management, immunotherapy, or allergy shots, can gradually build tolerance to specific allergens over several years.