The effectiveness of castor oil to encourage the onset of labor is questionable. It is generally considered safe, although there are some who believe that it increases the risk of meconium passage in the infant. It has not been well studied, which is surprising considering how long this old remedy has been in use. I would suggest that any pregnant woman who is considering trying to induce her own labor by this or any other method, including herbs, be sure that her baby is ready to be born. Sometimes there are reasons why labor does not start when we think it should, including a baby that hasn't gotten into a good position to be born from.
Castor oil has a very unpleasant taste and texture.
There are many recipes for disguising this. There is also a commercially prepared emulsified form with a peppermint taste. The recommended dosage for encouraging labor ranges from 1 TBS to 4 OZ, depending on who you talk to about it. Some use a single dose, others repeat the doses. Methods of disguising the taste include mixing it with root beer and ice cream, sucking on an ice cube first, making a slurpy with juice, crushed ice and the castor oil in a blender, adding baking soda, adding vodka, and combinations of all the above.