Final Answer:
The first contact of allergy is sensitization, where the immune system recognizes and reacts to a foreign substance (allergen). After multiple exposures, the immune system becomes hypersensitive, leading to exaggerated responses upon subsequent encounters with the allergen.
Step-by-step explanation:
Allergies begin with sensitization, the initial contact between the immune system and an allergen. During this encounter, the immune system identifies the substance as harmful, triggering the production of specific antibodies, such as immunoglobulin E (IgE). IgE antibodies attach to mast cells and basophils, priming them for future encounters with the same allergen. This sensitization process may not cause noticeable symptoms initially.
Upon subsequent exposures to the allergen, the immune system is primed for an exaggerated response. When the allergen binds to IgE antibodies on sensitized cells, it triggers the release of various chemical mediators, including histamine. Histamine and other substances cause the symptoms associated with allergies, such as itching, sneezing, and swelling. The severity of the reaction can vary, ranging from mild discomfort to life-threatening anaphylaxis.
Repeated exposures can further intensify the allergic response as the immune system becomes more sensitized. This phenomenon is known as allergic sensitization or hypersensitivity. Over time, the immune system may recognize additional allergens, broadening the spectrum of substances that can induce allergic reactions. Managing allergies often involves identifying triggers, avoiding exposure, and, in some cases, using medications to alleviate symptoms or undergoing desensitization therapies.