Library · Disease
Drug allergy
Make it clearer
When a medication causes harm, that is called an adverse reaction, and there are two very different kinds. Type A reactions are the ones that can be anticipated from what the drug does by design. Type B reactions are the ones those known properties do not predict, and that is where drug allergy lives: it is produced by the immune system, not by the pharmacology of the product.
The immediate form follows a clear sequence. On the first exposure the body makes immunoglobulin E specific to that drug, an antibody that stays anchored on the surface of mast cells and basophils, two defense cells loaded with inflammatory substances. When the person receives the medication again, those cells empty all at once and release histamine, leukotrienes, prostaglandins and other mediators. The body remembered the drug's face and reacts on the second visit.
It helps to keep the proportions in mind: only 6% to 10% of all adverse reactions are hypersensitivity reactions. And not all of them are immediate: those mediated by T lymphocytes, another kind of defense cell, show up late rather than right away.
In brief
A drug allergy is a type B adverse reaction: it is not predicted by the drug's pharmacologic properties but is produced by the immune system.
In the immediate form, the first exposure generates immunoglobulin E that settles on mast cells and basophils; on re-exposure, those cells release histamine and other mediators.
The body remembered the drug's face and reacts on the second visit.
Only 6% to 10% of adverse reactions are hypersensitivity reactions, and those mediated by T lymphocytes appear late.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingAdverse Drug Reactions, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingType I Hypersensitivity Reaction, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated