Suplatast tosylate is primarily used as an immunomodulatory agent in the treatment of allergic conditions. It works by suppressing the production of Th2-type cytokines, which play a key role in allergic responses. This makes it effective in managing symptoms of allergic diseases such as bronchial asthma, atopic dermatitis, and allergic rhinitis. In clinical use, it helps reduce the severity of skin inflammation and itching in patients with atopic dermatitis, especially in cases where standard therapies are not sufficient. For allergic rhinitis, it alleviates nasal congestion, sneezing, and runny nose by targeting the underlying immune response rather than just symptoms. It has also been studied for use in eosinophilic disorders due to its ability to lower eosinophil levels in blood and tissues. Because of its favorable safety profile and oral administration, suplatast tosylate is considered a useful long-term treatment option in chronic allergic conditions, particularly in pediatric and adult populations in Japan and some Asian countries where it is approved.