Merino smells

Could it be the wool is causing you to sweat more then the cotton?

Wool will smell, it just wont smell or hold the smell like synthetics. I can be a dirty sob at times, last year I wore a pair of SW midweight long underwears almost everyday and only washed them once every few weeks and never had trouble with them. But I did notice that when wearing a light weight smart wool tshirt I would get slight body odor more so than if i was wearing cotton underwear and tshirt over the top.

edit: nm, i didnt notice you said it was holding the smell.

This is a new one to me, I am a moderate sweater and only require a light application of Mitchum's Unscented every couple of days to remain BO free. Yet, if I put on the MEC synthetic top(s) I bought, even WITH thorough bathing in hunter's descenting soap and lots of Mitchum's, I notice an odour within an hour or slightly more.

However, I can wear a merino T under the hottest conditions hiking, sleep in it and remain odour-free for a couple of days. Cotton will not do this and tends to "stink up" and so I now use merino almost exclusively.

I suspect that this is just due to differences in body chemistry and "maybe" in the introduction of some synthetic fiber into the merino cloth used in MEC shirts? It is kinda a pita, tho', as merino just rocks in bush usage. All ya can do is Mitchum's Unscented, I guess!

You could try grinding up some of the crystal stick deoderant and disolve it in some water then spray it on your shirts pits. Maybe that will help supress the bacteria growth?