What typically occurs upon first exposure to a new allergen?

Upon first exposure to a new allergen, the body's immune system recognizes the substance as foreign and begins to mount a defense against it. This initial contact does not usually provoke an immediate allergic reaction, rash, or anaphylactic shock; rather, it demonstrates a sensitization process. During this first encounter, the immune system produces specific immunoglobulin E (IgE) antibodies. These antibodies do not cause noticeable symptoms but prepare the immune system for potential future exposures to the allergen.

In subsequent exposures, if the same allergen is encountered again, the immune system is primed to react more aggressively, potentially resulting in an immediate allergic reaction, rash, or even anaphylaxis, depending on the individual's sensitivity and the severity of their allergy. Understanding this process is crucial for recognizing how allergies develop over time and why some individuals may initially show no signs of an allergic reaction despite being sensitized to an allergen.