Hypersensitivity reaction to the ingestion or injection of a substance (a protein or drug) resulting from prior contact with a substance WordNet 3.0 & Open English WordNet

Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. Wikipedia

Severe allergic reaction Wikidata

A rare but life-threatening whole-body allergic reaction. Symptoms may appear quickly and include difficulty breathing, swelling of the throat or other parts of the body, rapid drop in blood pressure, dizzi ness, or unconsciousness. Anaphylaxis can be triggered by foods, drugs, insect stings, or exertion. OmegaWiki

Extreme sensitivity to a substance such as a foreign protein or drug. Wiktionary