Which of the following indicates a severe allergic reaction in an emergency?

A severe allergic reaction, also known as anaphylaxis, involves critical symptoms that can pose a life-threatening situation. Swelling of the throat is particularly indicative of this condition, as it can obstruct the airway and impede breathing. This swelling can lead to difficulty swallowing, speaking, or breathing, which requires immediate medical attention.

While itchy skin can occur during an allergic reaction, it is generally less severe compared to the implications of throat swelling. Red eyes might result from allergies but are not reflective of a severe response. Similarly, common cold symptoms may resemble certain allergic reactions but do not signify a serious allergic crisis. Therefore, swelling of the throat is a clear indication that immediate action and medical care are necessary to address the threat to breathing and overall wellbeing.