TSA letter from Doctor

Here's the letter that our doctor wrote for us to present to TSA if we have any problems:

"To whom it may concern,
xxx is a 16 month old child with feeding difficulties and poor weight gain.  Currently he is doing very well on rice milk.  Due to his feeding intolerance to other formulas, it is most important that he continues on the rice milk.  Please permit his family to bring rice milk on the flight".