The colour of our hair depends on the concentration of melanin pigment. Gray hair has less amount of melanin pigment. Some of the reasons for graying of hair are as follows:
1. Genetic factors: Genes control the deposition of melanin pigment in hair cells.
2. Melanin pigment is present in the melanocyte cells which are present in the hair bulb and along the bottom of the skin. Melanocytes pass this pigment to keratinocytes which produce keratin protein, the chief component of hair. But sometimes, these melanocytes become inactive and cause the graying of hair.
3. Excessive chemical action.
4. Frequent change of pH.