Castor oil is touted by many as a natural treatment for hair growth, however, there is no way to determine how long it makes a person's hair grow within a month. The length of hair growth is directly related to heredity.
Many people use castor oil for growing hair longer. The oil is a natural product that comes from the castor bean plant. So far, there is no scientific proof that backs up claims that castor oil has any effect on hair growth. On the other hand, there is lots of anecdotal evidence that the oil does have some benefits for the hair.
Hair is often damaged by over-processing with chemicals, dry scalp and split ends. Castor oil contains omega 6 fatty acids, protein and vitamin E, which are all considered healthy for hair. The scalp and hair shaft are in constant need of moisture. When castor oil is applied to the hair and scalp, it provides natural moisturizers and protein, which can help prevent the hair from falling out of the scalp.
Each person experiences monthly hair growth at a different rate. Since using castor oil causes the hair and scalp to become healthier, it can appear that the oil is stimulating hair growth. The hair is actually growing at a normal rate due to its healthier state.