Leukotrienes are chemical compounds produced by the body that play a crucial role in the immune response. They are derived from fatty acids and are primarily involved in inflammation and allergic reactions. By promoting the contraction of smooth muscles and increasing blood vessel permeability, leukotrienes help to direct immune cells to sites of infection or injury. These compounds are particularly important in conditions like asthma and allergic rhinitis, where they can contribute to symptoms such as bronchoconstriction and nasal congestion. Medications that block leukotriene receptors, known as leukotriene receptor antagonists, are often used to manage these conditions effectively.