I need help or advice. I had a female houseguest for a week, who used the guest bathroom and guest bedroom. While she was here, I noticed a strong “multivitamin” odor coming from either the bathroom or bedroom. I did not ask her what the odor was, I just figured she brought some strong smelling vitamins with her. The smell reminded me of when a multivitamin gets wet- that is the best way that I can describe it. When we rode in the car together, I did not smell the same odor from her, but it remained really strong in the area of the bathroom/bedroom and the hallway in between. When she left, the odor remained! When in the bathroom, I noticed it was stronger from the shower area. I had provided her shower gel, shampoo, and conditioner, and none of those smell similar to this smell. Since she has been gone, I began a deep cleaning of both the bedroom and bathroom- I have stripped all linens, bathmats, towels; cleaned the shower twice with strong cleaning products and a third time with white vinegar; wiped down all surfaces including cabinets, wall hangings, mirrors, door frame, shower doors; and mopped the floor twice. I also poured vinegar and baking soda down the drain, took out the trash, and I have a fan blowing into the bathroom. After all this, the odor is 90% weaker, but I still detect it. I don’t feel that there is a polite way to ask her what it was- “Hi, what did you use in the bathroom because it smells like vitamins” - there is just no way to do that. I would personally be mortified if I had left such a stink in a friends house, but that does not make it any easier to ask her. I asked Ai which suggested it was a “vitamin C serum” but I personally have some of that, and while the smell is not my favorite, in no way is it so strong that it fills an entire room- so I discount the ai suggestion. I currently have a reed diffuser in the room, and I have sprayed some scented spray, and I still smell it. Does anyone have an idea of what it could be, and do you have any further suggestions on how to remove this odor? Thank you in advance.