In a letter to President Trump, the spokesman, Rich Danker, said moves to allow the sale of flavored e-cigarettes would enhance their appeal to children.

The agency’s top food official will step in as acting commissioner, after Dr. Makary’s tumultuous run as the nation’s top food, drug, tobacco and medical device regulator.

President Trump chose Cameron Hamilton to direct federal disaster response. As acting head of FEMA last year, he had opposed abolishing the agency and was ousted.