A class of drugs known as cysteineyl leukotriene receptor-1 (CysLT1) antagonists is prescribed to treat allergic rhinitis and asthma. various medications function by preventing leukotrienes, which are inflammatory chemicals implicated in the pathophysiology of various illnesses, from doing their job. Due to its efficiency and tolerance, one of the well-known CysLT1 antagonists that has been utilized extensively is montelukast. Orally given, montelukast is a highly bioavailable antagonist of the CysLT1 receptor that is both selective and competitive. It is quickly absorbed from the digestive system after consumption, peaking in plasma concentrations after 3–4 hours. The ease of once-daily dosage made possible by this pharmacokinetic profile helps patients stick to their treatment plans. The capacity of montelukast to prevent leukotrienes from attaching to the CysLT1 receptor is its main mode of action. By doing this, it stops leukotrienes' downstream effects, which include the recruitment of inflammatory cells, smooth muscle contraction, and vascular permeability. This improves lung function and asthma symptoms by reducing airway inflammation and bronchodilation. It relieves sneezing, itching, and nasal congestion associated with allergic rhinitis. Clinical research has shown that montelukast is effective in treating asthma in both adults and children. It is applied as maintenance therapy to enhance asthma control and avoid exacerbations of the condition. When used in conjunction with inhaled corticosteroids, montelukast has significant anti-inflammatory and bronchodilatory benefits. Moreover, studies have demonstrated that montelukast has a low incidence of side effects and a favorable safety profile. Headache, stomach issues, and upper respiratory tract infections are the most often reported adverse effects. Although they are uncommon, neuropsychiatric adverse events, such as agitation, hostility, and suicidal thoughts, might be considered serious adverse events, especially in children and adolescents. Thus, it is advised to monitor closely, particularly in these populations. To sum up, montelukast and other CysLT1 antagonists are helpful in the treatment of allergic rhinitis and asthma. They are significant alternatives to other medications or supplemental treatment for individuals who need something more than inhaled corticosteroids because of their mode of action, effectiveness, and favorable safety profile.