You don't.
Killing things in the human body is for killing cancer growths, parasites like disease germs, worms, fungi and so on. Ants in a human body would either have been swallowed, in which case they usually would be dead already, or would die soon, or they would be in a dead limb or wound or the like and not of any medical importance.
If you are talking of ants, say a colony of fire ants, that have attacked a human and are all over the body and clothes, then remove the clothes where necessary, and scrape the skin where the ants are with the back of a knife or some similar and harmless scraper; it is faster than picking them off. If there still are lots of ants around while you are dealing with them, then while you work get the victim into water to stop the ants (with plenty of added detergent if possible, but don't waste time getting the detergent). Then deal with any stings or bites.
Possibly you are thinking of stories like those of witch doctors or shamans who let ants in or out of human bodies, but one gets lots of nonsensical stories of that kind.
The real stories are far more interesting.
Why,yes they can.
a fire ant usually feed on plants and are located in open areas, usually living in a big mound of dirt. a fire ant, normally called red ants can kill an human if there is enough of them.
No they cannot, elephants can merely step on ants to kill them while it would take years for ants to eat elephants.
Yes, apparently beer does indeed kills ants. Beer is listed as a home remedy in killing and ridding homes of ants.
Ants will bite while a human is sleeping because they will attack anything that is not in motion for any amount of time.
yes that eat insets and some time bite human and kill them
yes. it happened to me lots of times.
ants kill anything that is small enough for them to get there mandibles on
hell yeah thats how i kill them ;)
sometimes
Imidacloprid will kill ants that are in the area where it is applied. It will not kill their colony unless the chemical kills their queen.
Onions alone are not known to kill ants. A combination of onions, soap, garlic, cayenne, and water is a solution people claim work to kill ants.