Used to measure interleukin-4 (IL-4) levels in human biological samples such as serum, plasma, or cell culture supernatants. It is widely applied in immunology research to study T-cell responses, allergic reactions, and inflammatory diseases. The kit helps in diagnosing and monitoring conditions like asthma, atopic dermatitis, and other Th2-mediated disorders. It is also used in clinical trials and drug development to evaluate immune modulation effects.