On the days when he does not shower, does he wash his armpits thoroughly? He needs to be doing that, especially at this time of year, and using a good antiperspirant/deodorant. Wash the offending articles in bio detergent using one of the products mentioned (eg Vanish). Put a good glug of white vinegar in the final rinse. It kills germs and bacteria and also acts as a fabric conditioner. Line drying is preferable, as sunshine is a natural getm-killer, but rather than use a tumble dryer, I would hang washing on a clothes horse overnight in a closed room, with a dehumidifier running. It works well for me.