I make mine using deer feed corn. I use muslin or such for the actual bag, then also make a cotton cover-like a pillow case- so it can be washed. The corn holds the heat longer than the smaller grains, I find. But have also used flax seed, rice. :)

Our sewing group for the hospital makes these bags. We put rice in them, but a friend who also makes them uses buckwheat.

I bought our oldest Granddaughter a long thing at Walgreens for to heat for her headaches. Has two blue plastic rings, one on each end. It will go around her neck or put on her head. It usually helps her headaches, not always if they are real bad.
I don't know what is in it, I would think plastic beads. Doubt any that could bought in stores would have food stuff of any kind.

These are really nice for sinus headaches. Bugs will get in them if you don't store in a plastic baggie or container. I have sinus problems and TMJ. I often put rice into an old athletic sock and place it into the microwave for 1-2 minutes. Be careful not to get burned! The moist heat is soothing.

I know some folks use deer corn... its sold at Farm and Garden places... its untreated corn and works well!!

Must need more coffee... I read this as store in a cookie jar. I got my morning giggle thinking of the expressions when someone opens the jar and finds only the bag!

I have made them using rice however my family does not like the rice smell. I purchased one in Gatlinburg made with cherry pits...I really like it alot. When I made the rice bags I did them in muslin and made little pillowcase type covers out of pretty flannels. Very cuddly. I keep thinking I will take the cherry pit bag apart and put the pits in muslin make a flannel cover..

Thanks to all for responding. I now have a lot of good ideas. Thanks so much