Articles on Yahoo! Health tend to hang around the Internet for a while. That’s why a mistake like this can be so damaging: Innocent readers might think this is correct because the article was written by “editors”:
It’s not correct because awhile is an adverb and only a noun or noun phrase (like a while) can be the object of a preposition. So, correct prepositional phrases include: in a while, for a while, and after a while.