Subjects were asked to follow the testing protocol shown in
Figure 1. Subjects conducted their first test of each repellent by
inserting the treated arm into a test cage for one full minute every
five minutes. If they were not bitten within 20 minutes, then the
arm was reinserted for 1 full minute every 15 minutes, until the
first bite occurred. On the basis of this initial complete-protection
time, the subject’s next two tests of that particular repellent were
conducted as follows: if the repellent had initially worked for less
than 20 minutes, the subject placed his or her arm in the cage for
1 minute every 5 minutes; if the repellent had initially worked for
20 minutes to 4 hours, the subject placed his or her arm in the
cage for 1 minute every 15 minutes; and if the repellent had initially
worked for more than 4 hours, the subject placed his or her arm
in the cage for 1 minute every hour (up to 4 hours). If a repellent
was still working after 4 hours, then the subject continued to
place his or her arm in the cage every 15 minutes thereafter, until
the first bite occurred. If at any point during testing, subjects
noted mosquitoes landing but not biting (a behavior that typically
occurs when the efficacy of a repellent begins to wane), then
the intervals between insertions were decreased to five minutes.