Kryptonite. Yeah, and just about everything else during and following AT thruhikes. Thruhiker stink is unique... that old cheese fragrance you might experience in the vicinity of a crusty, fusty, musty vagabond. Everyone seems to struggle with it before giving up. I have been known to carry incence sticks for those times in a shelter when the atmosphere around my fellow hikers makes the eyes water. (That's the best argument for staying away from shelters IMHO.)
Paul: Sure, sunlight and a good airing will certainly help - and are often enough for such items as sleeping bags (even after thru-hikes). Shoulder straps are the main culprit since they catch underarm efluvium, and even closed-cell foam becomes swingingly odiferous within a few weeks.
A good airing in the Texas sun combined with time will reduce the immediate eye-watering, gag-inducing outgassing, but the substances that produce it - which are uniquely resistant to washing and bleaching IME - continue to lurk, only to be reactivated on the first warm day on the trail.
Seriously, MyraZyme is the only thing I have found that actually removes, destroys, and annihilates hiker stink. It now goes in the bump box on thruhikes.