Factors that attract and repel mosquitoes in human skin

Abstract

We have surveyed large numbers of men to find individuals unattractive to the Aedes aegypti mosquito. In biting, experiments, we tested 838 volunteers and found one clearly less attractive than others. In mosquito probing experiments (the probing time 50 test, a more sophisticated method of measuring attractancy), we surveyed 100 men. We found three significantly less attractive and two significantly more attractive than the control subject. In attempting to determine the mechanisms of attractancy, we studied human sweat and skin lipid (obtained with diethyl ether washings). The fractions were isolated and assayed in the olfactometer. Sweat contained attractive substances which could be extracted with ether and ethyl alcohol and which were lyophilizable and dialyzable. In the olfactometer the skin lipids were repellent. The fractions responsible for this are presently being isolated. It is postulated that variations in attractiveness of humans to mosquitoes may at least be in part determined by the balance of these attractant and repellent substances.