Which of the following would NOT be a sign of a severe allergic reaction?

In the context of severe allergic reactions, the signs and symptoms typically manifest due to the body's immune response to an allergen. Difficulty breathing, swelling of the face and neck, and nausea and vomiting can all be direct consequences of severe allergies, such as anaphylaxis.

Difficulty breathing arises from airway constriction or swelling, which is a hallmark of a severe allergic reaction. Swelling of the face and neck indicates angioedema, often related to anaphylactic responses. Nausea and vomiting can occur due to the ingestion of the allergen or as a systemic reaction to the allergenic triggers.

A persistent cough, while it can occur in various medical scenarios, including respiratory infections or other non-allergic conditions, is not a specific indicator of a severe allergic reaction. Coughing alone does not signify the acute and life-threatening symptoms associated with anaphylaxis, making it less relevant when assessing for severe allergic reactions.

Thus, the absence of these more acute symptoms in a persistent cough underlines why it would not be considered a sign of a severe allergic reaction.