IL-13 is a cytokine, which is a type of protein that plays a crucial role in the immune system. It is primarily produced by a subset of immune cells known as T-helper 2 cells. IL-13 is involved in regulating allergic responses and inflammation, particularly in conditions like asthma and allergic rhinitis. This cytokine works by promoting the production of IgE, an antibody associated with allergic reactions, and stimulating the growth of certain immune cells. Additionally, IL-13 helps in the repair of tissues but can also contribute to chronic inflammation when produced in excess, leading to various health issues.