Answer:
It is the great nemesis of the lactose intolerant.
Hard to catch, easy to hold. Can't be seen, unless it's cold
I have legs but never walk, I may have flowers but no soil, I hold food but never eat.
I move without wings, Between silken string, I leave as you find, My substance behind.
A seed am I, three letters make my name. Take away two and I still sound the same.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?