How does singulair help asthma patients? what's it's mechanism?

Singulair is a leukotriene inhibitor. Leukotrienes are chemicals your body releases when you breathe in an allergen (such as pollen). These chemicals cause swelling in your lungs and tightening of the muscles around your airways, which can result in asthma symptoms. So this medication is more effective in extrinsic or allergic asthma.

Singulair blocks natural substances called leukotrienes that narrow your bronchial tubes and thus it prevents wheezing. It also blocks nasal membrane swelling. Meds like singulair are slower than antihistamines in reaching a full effect.