We all lose microscopic skin pieces from all over the body, including from the scalp, daily. Bacteria and other little `guys` live on /break down these. Your scalp also produces oils etc. even on bald heads.... all this material can/does accumulate under tape/glues....oils and sweat will be absorbed by lace... acids in sweat will weaken/damage any base materials over time, including poly. As a matter of hygiene / health you should give your lace a rinse each time you de-bond, otherwise you`ll risk [at the very least] unpleasant odours from a build-up of such material....just sit it in a sink of lukewarm water to which you`ve added some shampoo....give it a few minutes and rinse it off/dry it .... re-bond when the lace is totally dry.