Everyone's physical condition is different, and their secretions are different.
The smell of human body is produced in the process of human metabolism, which is related to the substances metabolized by human body. Substances metabolized by the human body can be roughly divided into three categories.
The first category is lipid substances, such as sebum and sweat secreted by the skin. Sebum is what we usually call oil on the skin surface, which will form a sebum film on the skin surface. Sebum will be oxidized when exposed to air for a long time, forming oxidized lipid and emitting peculiar smell. We know that sweat also smells.
The second category is protein substances, including our excreta. When protein is fermented, its flavor is much stronger than lipids.
The third category is some sugars, including exhaled carbon dioxide, and some are organic acids.
All three substances secreted by the human body will stink.