Evidence Level
Propolis has a growing clinical evidence base. Cohen et al. (2004) conducted a well-designed RCT showing propolis significantly reduced upper respiratory infections in children during winter. Sforcin (2007) published a comprehensive review of propolis's biological properties, confirming its antimicrobial spectrum against bacteria, viruses, fungi, and parasites, plus its anti-inflammatory and immunomodulatory effects. CAPE has emerged as a particularly interesting compound, with potent NF-kB inhibition that has attracted attention from cancer researchers as well. The main challenge in propolis research is standardization — propolis composition varies by geographic origin, bee species, and plant sources, making comparison across studies difficult. Brazilian green propolis and European poplar-type propolis are the most studied varieties.