Which of the following signs may indicate a severe allergic reaction?

A severe allergic reaction, also known as anaphylaxis, can present with critical symptoms, one of the most concerning being the swelling of the lips, tongue, or face. This swelling, referred to as angioedema, can severely obstruct the airway and lead to breathing difficulties, making it a potentially life-threatening emergency requiring immediate medical attention.

Recognizing this type of swelling as a hallmark sign of a severe allergic response is vital for effective intervention and management. Other symptoms, while they may indicate an allergic reaction, do not carry the same immediate risk to life as the swelling in the airway can, which elevates the urgency of the situation.