Final answer:
It is true that adverse reactions can be localized or systemic. Mild localized allergic reactions can cause symptoms such as itching or hives, whereas systemic reactions like anaphylaxis are severe and potentially life-threatening, often requiring emergency treatment with epinephrine.
Step-by-step explanation:
True. Adverse reactions to allergens can indeed be localized, such as pain, swelling, and redness at the injection site or may present as systemic symptoms like fever, malaise, rash, drowsiness, or irritability. In the case of Type I hypersensitivity reactions, these can be either localized (e.g., hay fever, hives) or systemic, the latter of which is referred to as anaphylaxis or anaphylactic shock, which may involve symptoms such as dangerous drop in blood pressure and severe swelling that can be life-threatening.
Allergic responses are a result of an over-reactive immune system. A mild localized reaction might involve symptoms such as watery, itchy eyes and sneezing. On the other hand, anaphylaxis is a severe systemic reaction that can lead to life-threatening symptoms such as severe throat swelling and a substantial drop in blood pressure and requires immediate medical intervention typically with injections of epinephrine.
Skin testing is often used by allergists to identify allergens in Type I hypersensitivity. This testing involves injecting allergen extracts into the skin and observing for a reaction, known as the wheal and flare response, indicative of a localized allergic reaction.