Propolis

Propolis is the glue honeybees make to build, repair and protect their hives, made from partly digested tree resins mixed with beeswax [1][10]. More than 800 compounds have been reported in it, and its make-up varies with region and season: temperate poplar-type, Brazilian green, red and other types differ chemically, which makes it hard to standardise [8].

Australian propolis is unusual. University of the Sunshine Coast researchers found propolis from subtropical eastern Australia had a chemical profile distinct from European poplar propolis; in the lab it killed Staphylococcus aureus but had no effect on Klebsiella or Candida yeast [6]. Kangaroo Island propolis comes from a native sword sedge and contains compounds not described before [7].

The best human trial tested a combination. In a double-blind study of 60 people aged 14 to 34 with mild to moderate acne, a cream with 20% propolis, tea tree oil and aloe vera reduced the acne severity index by 66.7% over 30 days, compared with 49.7% for an erythromycin cream, and was compared with a placebo too [4]. Because of the tea tree and aloe, the benefit can't be credited to propolis alone. A meta-analysis on wounds included 43 studies, but 40 were in animals [5].

Allergy is the best-documented fact. In European patch-test studies, 1.2% to 6.6% of people tested react to propolis, and it frequently cross-reacts with balsam of Peru, colophony (rosin) and fragrance mix [1]. In a Swedish study of 722 people being investigated for dermatitis, 6.2% reacted to at least one propolis sample, and 43% of those also reacted to balsam of Peru [2]. Reviewers note that propolis cosmetics are an infrequent cause of new sensitisation; many reactions are in people already allergic to fragrance [3].