I know plenty of you have raised teenagers so I’m hoping some of you will know what this is.
He’s 15. Showers every day including washing hair. Brushes his teeth once a day at least, twice if he remembers in the morning. 
He uses roll on deodorant daily. He spends his days barefoot and the shoes he wears out of the house are kept downstairs. His clothes are washed daily. He has a laundry basket that they stay in and it is emptied every evening. There are no dirty pants/socks/anything lurking in his room because I completely stripped the room bare last weekend, moved all furniture, washed absolutely everything, including his mattress, all surfaces, bed linen, curtains. The whole lot. He doesn’t wear pyjamas and the offending smell does transfer to his bedsheets. So it’s coming off his body but I just don’t know how! He is washed every day. It is a bodily smell but doesn’t smell like BO. It is horrible though and his room is small and gets warm and stuffy so the smell is strong. His window and curtains are open for a few hours a day. I would have them open all day but he spends a lot of time in his room and likes to close them. The smell is from him but if I sniff him he doesn’t smell. If he leaves his bedroom door open the smell comes through the house.
Please help. I feel awful constantly reminding him to open his windows and asking to sniff his hair to see if it’s clean but we really need to get to the bottom of this. The smell is really horrible.
Can anyone shed any light and/or recommend some products he/we can use to combat this?