Comments and reply on; Stjernberg L, Berglund J. Garlic as an insect repellent

Objectives: To study if Swedish marine conscripts are a population of high risk to tick-bites and tick-borne diseases and if tick-bites could be prevented by consumption of garlic. Design: Prospective, randomised double blind intervention trial. Subjects: 100 individuals from south-eastern Sweden in military service during 1998. Interventions: The survey participants consumed 1200 mg Allium sativum/placebo for eight weeks, had a wash-out period then changed to placebo/Allium sativum consumption for another ten weeks. All participants had uniform clothes, the same diet, participated in similar activities, stayed equal time in tick-endemic nature etceteras. Main outcome measures: Tick-bites were registered in a diary-sheet after daily inspection of the skin. Results: Totally 286 tick-bites were registered by the participants. On average the participants registered 0.2 tick-bites per week during military service compared to 0.03 tick-bites during leave. Results shows significant reduction in tick-bites when consuming garlic compared to placebo (p<0.05). Furthermore, during placebo consumption, a greater number of the participants were bitten by ticks (incidence per 10 weeks = garlic, intention to treat 0.5, per protocol 0.6, placebo, intention to treat 0.5, per protocol 0.7). Swedish marine conscripts are at high risk of tick bites during military service. Preventive measures, including vaccinations against tick-transmitted diseases, should be considered. However, our results suggest that garlic may be considered as a tick repellent for individuals and populations at high risk for tick bite, rather than other agents that might have more adverse effects.