Looking for a specific book for a young reader, can't remember the title, pl

Question: Looking for a specific book for a young reader, can't remember the title, please help!!?

My son was reading one of my old books and lost the book!. The story is set in San Francisco, a son lives with his mom and they run a boarding house!. He meets a strange traveling salesman that gives him this "magic juice" which the kid rubs on his shoulders and grows wings!.!.

He was in the middle of the book so it is driving us both nuts!. Www@QuestionHome@Com

Best Answer - Chosen by Asker:

The book is called Black and Blue Magic by Zilpha Keatley Snyder!.

I hope that helped!Www@QuestionHome@Com