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Background: It is well known that eosinophilic airway inflammation develops after allergen challenge in sensitized humans and animals. However, the detailed time course of suppression of early eosinophilic airway inflammation by pharmacological agents given just after challenge has not been discussed. Therefore, we aimed to evaluate the time course relationship of the suppression of peak eosinophilia by anti–cytokines and pharmacological agents given several hours after the aerosol challenge by a therapeutic approach. Methods: We used crude mite extract as an allergen to create a sensitization and inhalation challenge, and performed bronchoalveolar lavages (BAL) after the inhalation challenge to observe the degree of eosinophilic airway inflammation in guinea pigs. Various anti–cytokines (anti–IL–3 and anti–IL–5) and pharmacological agents (dexamethasone, theophylline, and roxithromycin) were given within several hours after the acute aeorosol challenge to evaluate the suppressive effect on peak eosinophilia in BAL fluid, which occurred 24 h after the challenge. Results: Our results show that anti–IL–5 and dexamethasone, given within 4 and 8 h after the inhalation challenge, respectively, inhibit the acute allergen–induced peak eosinophilia in BAL fluid. However, anti–IL–3, theophylline, and roxithromycin had no effect on peak eosinophilic airway inflammation after challenge. Conclusion: These observations suggest that several hours are needed to complete the process of cytokine–induced recruitment of eosinophils from the blood to the airways after acute allergen challenge. This may be the optimal time to administer anti–cytokines and dexamethasone to attenuate the subsequent eosinophilic airway inflammation after acute allergen–induced asthmatic attacks. [ABSTRACT FROM AUTHOR]