Inflammation is a key characteristic of asthma, and leukotrienes function as chemical mediators (a chemical that acts as a messenger in the body) in the inflammation process.

They are byproducts of arachidonic acid, an essential fatty acid found in the outer membranes of mast cells in the body. When activated, leukotrienes constrict the muscles surrounding the airways (bronchospasm) and cause the production of excess mucus, which can clog the airways (airway wall edema).

In addition, leukotrienes attract white blood cells called eosinophils, which also release some of the major chemical mediators involved in bronchospasm. As a result, the airways swell and fill with mucus, reducing air flow.