A mustache.
Lines 1-2: These lines refer to a handlebar mustache.
Lines 3-4: Everyone can see someone else’s mustache. One with a mustache can use a mirror to see their own mustache.
Lines 5-6: If no preventative action (i.e., shaving) were taken to prevent the growth of a mustache, many people would have one.
Lines 7-8: A kid may have a milk mustache, which is made of milk; a real mustache is made of hair.
Source…