The effect of adenosine on tactile allodynia (secondary hyperalgesia) was studied in 6 healthy volunteers, using a double-blind, placebo controlled, cross-over design. Tactile allodynia was induced by topical application of mustard oil on the skin of the volar aspect of the forearm. Adenosine (50 micrograms kg-1 min-1) or saline was given intravenously for 20 min before the mustard oil application and continued for another 50 min. The tactile allodynic areas for brush and von Frey filament stimulation were both significantly reduced by approximately 50% during adenosine infusion, compared with placebo. The threshold for eliciting allodynia with von Frey filaments was not influenced by adenosine. The study shows that adenosine can reduce the area of mustard oil induced tactile allodynia.