Which leukocyte is primarily involved in allergic reactions?

Eosinophils play a significant role in the body's response to allergic reactions and parasitic infections. These white blood cells are characterized by their ability to produce inflammatory mediators such as histamines and other substances that can enhance the immune response during an allergic reaction. They respond to allergens by increasing in number and releasing these mediators, which help to combat perceived threats.

In the context of allergies, eosinophils are particularly involved in the inflammation associated with conditions such as asthma, hay fever, and eczema. Their primary function is to counteract the effects of allergens and help regulate the immune response, making them crucial in the context of allergic reactions.

While neutrophils are the predominant white blood cells that respond to bacterial infections and inflammation, and lymphocytes are central to adaptive immune responses, they do not play the primary role in allergies as eosinophils do. Basophils, though they also release histamines and contribute to allergic responses, are present in much lower numbers compared to eosinophils and are less involved in the typical allergic response. Hence, eosinophils are correctly identified as the leukocyte primarily involved in allergic reactions.