Possibly testosterone levels? Why do teenage boys stink worse than young boys or grownups? (I mention this because I have two boys... may need some lye soap) To aswer your question I don't know but probably has to do with hormones and phermone levels. Fight or flight reflexes are controlled by hormones such as adrenaline, and we know that testosterone makes a bucks neck swell. Anyways thats my best guess.