I'd heard about putting onion slices on my child's feet (in socks) to take down a high fever (over 102.5) but I was skeptical. Last week my entire family came down with the worst flu we have seen collectively and tylenol/motrin alternating was not taking down my 9 year old's fever significantly so I mentioned the onion thing to dh and he encouraged me to try it. It really worked. I coupled it with a dose of motrin (which had not worked solo for 2 days) and just put the slices in his socks. Within half an hour he was feeling better and cooler and within an hour he was near his normal temperature and able to sit up and read where he had been miserable and only able to lay in the bed and shiver.
Previously, I've tried socks dipped in cool water and wrung out then put on the feet along with cool cloths on forehead and neck and wrists. This works but nor for long and has to be redone all night. With the onions, my child was able to sleep all night and the fever took 8 hours to come back up.