Why do M&M's melt in your mouth but not in your hand ?

This is because there is a layer of sucrose between the outer shell and the inner chocolate. When you bite an M&M in half, you can see this white layer.

Even though they do tend to melt in your hand if you wait long enough, the M&M people like to tell you that the sucrose layer is why they don't.

M&Ms have a coating (notice gum acacia and dextrin in the ingredient statement) and a hard candy shell. The chocolate centers would easily melt in your hand if not for the shell and coating. Chocolate (actually the coca butter) melts at a temperature near body temperature. While the chocolate in M&Ms may melt, it melts encased within the hard candy shell, and not "on your hands".

Hm.. I think they melt in your hand, too after a short time, but they definitely melt quicker in your mouth because of the heat and of the special substance which brakes food down.

Put some in your hand and stand outside in Florida in August, beleive me they will melt!

I'm a mom. Believe me, M & Ms also melt in the hand! ;)

They melt in heat, so yes they melt in your hand.

They do melt in your hand.

your saliva (spit) breaks the bonds between the molecules of the outer shell (coating) then when your saliva touches the chocolate, the chocolate reacts to your saliva by melting.

Because they have a hard coating/shell on the outside. I like them too!

Obviously because of their hard candy shell.