Approximately how long may it take for ICS therapy to manifest its maximum protective effect through consistent daily use?

Two to four weeks

Unlike rescue inhalers which provide immediate symptomatic relief by rapidly relaxing smooth muscle, inhaled corticosteroid (ICS) therapy works by modifying the underlying biological process of inflammation. This process of down-regulating gene expression and reducing chronic swelling requires cumulative exposure. Therefore, patients must adhere to the prescribed daily routine even when feeling well, as the full benefit—the maximum protective effect that significantly reduces overall attack risk—is not instantaneous. It typically requires a sustained period of consistent administration, usually estimated between two and four weeks, before the full anti-inflammatory benefits are fully realized.