These shirts have been around for many years and as I recall , were supposed to be treated with a bug killer , not repellant , and allowed to dry 24 hours before wearing . What we used for treatment was called Perma Kill and it would kill any bug that landed on this shirt/jacket for up to 4 weeks after treatment . This jacket was so effective (with the treatment) that after prolonged use in a bug infested environment, it would dramatically reduce the population of biting bugs, especially if there were numerous people wearing them , almost to the point of erradication ! I remember that when this concept 1st came out , it was highly praised by world renowned outdoors people . and was scientifically tested and won awards for a best new product . It has obviosly stood the test of time .