Unsweetened natural cocoa powder is enriched with nutraceutical abundance of anti-asthmatic compounds theobromine and theophylline. Cocoa powder, which is prepared after removal of the cocoa butter, contains about 1.9% theobromine and 0.21% caffeine. Anecdotal reports indicate that regular consumption of unsweetened natural cocoa powder (UNCP), a common practice in Ghana, West Africa, has the potential to reduce the tendency of asthmatic episodes. In the present paper we studied the effect of regular ingestion of aqueous extract of UNCP on hematological and histopathological changes that occur in ovalbumin (OVA)-sensitized guinea pigs. OVA-sensitized guinea pigs were challenged with aerosolized OVA 1 hour after ingestion of 300 mg/kg (low dose) or 600 mg/kg (high dose) of UNCP for 35 consecutive days. Histopathological and haematological changes in the OVA-sensitized guinea pigs were evaluated. Both negative and positive controls with distilled water and prednisolone, respectively, were used. OVA-sensitized guinea pigs demonstrated concentration-independent reduction in immune response to aerosolized OVA. There were no histo-architectural changes in the bronchiolar smooth muscles of the treated groups. Unsweetened natural cocoa powder has potential anti-asthmatic properties when administered orally at the doses tested.