What does allergic mean?
"Allergic" is an adjective describing a state of heightened sensitivity in which the immune system reacts abnormally to a normally harmless substance — pollen, certain foods, animal dander, insect venom, or medications. A person described as allergic to something experiences symptoms ranging from sneezing and hives to, in severe cases, life-threatening anaphylaxis. The word also applies to the reactions themselves, as in "an allergic reaction," and it has developed a playful figurative use in everyday English: someone may say they are "allergic to mornings" or "allergic to drama," meaning they strongly dislike them. Grammatically, allergic almost always pairs with "to" — you are allergic to something rather than simply allergic. The underlying term is surprisingly young: "allergy" was only coined in 1906 by Austrian pediatrician Clemens von Pirquet, making "allergic" one of medicine's relatively recent contributions to everyday vocabulary. Its precision matters, since genuine allergies differ from mere intolerances in their immune mechanism and potential severity.
Having an allergy; exhibiting an adverse immune reaction to a particular substance.
"She is severely allergic to bee stings and carries an epinephrine auto-injector."
Almost always followed by "to" plus the trigger substance.
(Informal) Having a strong dislike or aversion to something.
"He jokes that he's allergic to early morning meetings."
Figurative and humorous; not appropriate in strict medical contexts.
The word 'allergy' wasn't coined until 1906 — before then, doctors simply had no name for the immune system overreacting.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of allergic
The word derives from "allergy," a term coined in 1906 by Austrian pediatrician Clemens von Pirquet from Greek roots: "allos" (other, different) combined with "ergon" (work, activity), originally describing an altered reactivity of the body. The adjective "allergic" followed soon after as medical understanding of hypersensitivity expanded. It shares its Greek root "ergon" with words like "energy" and "ergonomic," though those took a more general path into English.
Related word forms
How allergic is actually used
"Allergic" is always used predicatively or attributively with "to": one is allergic to something, not merely "allergic." The figurative sense ("allergic to hard work") is informal and humorous but widely understood. Medically, "allergic" specifically implies an immune-mediated response, so true food intolerances (such as lactose intolerance) are not technically allergies, though lay usage often blurs the distinction.
Easily confused with allergic
An allergen is the substance that triggers a reaction, while allergic describes the person or reaction affected by it.
Allergy is the noun naming the condition itself, whereas allergic is the adjective describing someone who has it.