What is a common symptom of an immediate hypersensitivity reaction?

An immediate hypersensitivity reaction, commonly referred to as an allergic reaction, typically manifests within minutes of exposure to an allergen. Flushed skin is a characteristic symptom of this type of reaction. The flushing occurs due to the dilation of blood vessels, which is part of the body's rapid response to the allergen, mediated by histamines and other inflammatory mediators released by mast cells.

This response can lead to other symptoms such as hives, swelling, or itching, but flushed skin is particularly recognizable and often occurs in conjunction with these other symptoms. In contrast, joint pain, fever, and smell sensitivity are more associated with other medical conditions or types of immune responses rather than being hallmark signs of immediate hypersensitivity reactions. Thus, flushed skin is a clear indicator of the body's immediate inflammatory response to allergens.