John R. Halliwill (IMAGE) University of Oregon Caption Work in John Halliwill's lab at the University of Oregon has found that overactive receptors to two histamines may be to blame for fainting spells that strike some people, even highly trained athletes, after rigorous exercise. Credit University of Oregon Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.