Which type of leukocyte increases during allergic reactions?

Eosinophils play a key role in the immune response, particularly during allergic reactions and parasitic infections. When an individual is exposed to allergens, such as pollen or certain foods, the body responds by producing IgE antibodies that trigger the release of chemical mediators. These mediators attract eosinophils to the site of the allergic reaction.

Eosinophils have specific functions that are critical in combating allergens; they can release substances that help to neutralize and break down allergens, as well as modulate inflammatory responses. Their presence is often significantly elevated in conditions like asthma, hay fever, and eczema, which are all manifestations of allergic responses.

In contrast, neutrophils primarily respond to bacterial infections, B lymphocytes are integral to antibody production, and monocytes are involved in phagocytosis and mature into macrophages in tissues. While all these cell types are essential components of the immune system, eosinophils are the ones specifically associated with increased activity during allergic reactions.