It is considered that early intervention for pollinosis relieves symptoms during the pollen season in Japan. Therefore, initiating medication prior to pollen dispersal has recently become a popular trend under the influence of the mass media. However, the actual benefits of this kind of early intervention during the peak of the pollen season have not been evaluated enough. We review a randomized placebo-controlled trial that was conducted to examine the efficacy of early intervention (before pollen dispersal) with the oral cysteinyl leukotriene receptor antagonist (LTRA) pranlukast against pollinosis symptoms in patients with allergy to Japanese cedar and cypress pollens in 2007. The subjects were treated with pranlukast or placebo for 4 weeks at the beginning of the cedar pollen dispersal season. Subsequently, all the patients received nasal steroid therapy concomitantly with pranlukast throughout the remaining period of the pollen dispersal season. The effects were evaluated by symptom scores based on allergy diaries and quality of life (QOL) scores as determined by the Japan Rhinoconjunctivitis Quality of Life Questionnaire. In the pranlukast-pre-treated patients, the nasal symptoms (paroxysmal sneezing, runny nose and nasal congestion) were improved during the early Japanese cedar pollen dispersal season. Subsequently, concomitant therapy with pranlukast plus nasal steroids for the rest of the pollen season significantly improved the symptom and QOL scores compared with the placebo-pre-treated patients. This study shows that LTRA administration to Japanese cedar and cypress pollinosis patients starting just before and continuing throughout the pollen dispersion season in high-risk communities is effective for improving the clinical symptoms and indicators of pollinosis. Further assessment of the efficacy of early intervention with an LTRA is required in comparison with other drug therapies, with consideration of the associated cost–benefit effectiveness.