A serious condition that can arise from a severe allergic reaction is:

A serious condition that can arise from a severe allergic reaction is swelling of the upper airway, known medically as airway edema or angioedema. This symptom can occur in response to allergens and leads to a narrowing of the airway, which poses a significant risk, potentially resulting in difficulty breathing or even respiratory failure. In severe allergic reactions, such as anaphylaxis, the rapid onset of swelling can obstruct airflow, making it crucial to recognize and treat this condition promptly.

In contrast, sneezing, watery eyes, and a runny nose are typically milder symptoms commonly associated with allergic reactions but do not indicate a life-threatening scenario. These symptoms are often part of allergic rhinitis and usually involve the body’s histamine response without resulting in airway obstruction. Therefore, recognizing the swelling of the upper airway as a critical condition emphasizes the need for immediate medical attention to manage a severe allergic reaction effectively.