Conversations about the worries of scents from head cement is something we used to talk about at the local fly club and some folks "pre-soak" their flys in water before use. The late Carl Hansen (Hansen's Glass Minnow) didn't use any cement on his flies.

Most recently I read this from one of Marv Taylor's articles in FAOL:

Tip #1- Avoid the use of any head cement or other chemicals when tying your wet flies.
I'm a firm believer that anglers leave "scent tracks" on almost everything they touch when fishing. Salmonids have superb olfactory senses. How else can salmon and steelhead find their way back to their place of birth, if they can't follow the scent of that tiny central Idaho stream as it mingles with the Salmon River, flows then into the Snake, finally to merge with the mighty Columbia River. Being able to pick up the scent of its home waters at the mouth of the Columbia and follow it home to that little creek in Idaho's Sawtooth range, boggles the mind. If they can do that, they sure as heck can detect the odor of head cement and other chemicals on our wet flies. I think this tip is actually worth about 20-percent.
(20% means it will improve your stillwater trout fishing by 20%!) In tip#2, he talks of hand washing to limit scents. Here is the link to the article:

http://www.flyanglersonline.com/feat...kes/part2.html

...I avoid using head cement on all wet flies. Marv Taylor's articles are really good reading..