If you or someone you know makes homemade play dough, it is important to remember that flour is a raw food and has been linked to serious food safety problems.
Iowa State University Extension offers this recipe that is cooked to heat the dough.
Homemade Play Dough
2 cups flour
1 cup salt
1 tablespoon vegetable oil
2 1/2 teaspoons cream of tartar
2 cups cold water
Mix all of the ingredients together and cook over medium heat for about 5 minutes stirring constantly. When finished, it will be the consistency of mashed potatoes. Divide it into 3-4 equal portions and add a few drops of different colors of food coloring to each. Kneading the dough will distribute the color and make it smooth. Store it in a freezer bag or air tight container and it will keep for a long time.