Why might someone smell bad?

The most common reasons for someone to smell unpleasantly probably are:

1. Exposure to a foul-smelling contaminant. That could include falling into a compost heap, getting covered with manure, standing by a burning garbage fire, getting covered with sewage or other non-potable water, etc. On a CSI episode, a CSI got water on him that came out of a purple fire hydrant. Another CSI told him to take a shower since the purple fire hydrants in their area use "greywater," which is not fit for bathing or drinking. Greywater is essentially what comes from sinks and washing machines, and while it should not contain body waste, it can still spoil and have an odor.

2. Challenges to personal hygiene. This may be because the individual has not received proper education regarding hygiene, but may also be situational, e.g. showers are hard for the homeless to find in winter.

3. Illness or pathology. Many illnesses carry with them an identifiable scent. For instance, there is bad breath that can come from dental disease. There is

4. Depression or other mental illness. Depressed people tend not to eat much, do much activity, socialize, or bathe that much. They are too down to want to do anything. So depression can lead to poor hygiene. That can lead to body odor, and body odor can indirectly cause depression to worsen. After all, who wants to be around someone who smells, even if they are the person who smells? Thus that can lead to more feelings of worthlessness. So it is a cycle. Then of course are those who are mentally handicapped or delusional, and they may need others to make them bathe or assist them. There are those who are more neurotic, schizoid, or who are on the autism/Asperger's spectrum. They might not really notice other people and don't really care how their hygiene affects others. They could care less either way, but others do care, and notice.

5. Loner lifestyle. Loners tend to not be around others as much, so they might not bathe or shower as much as others, since to them, that might be a waste.

Bear in mind that no one intentionally decides to smell bad.