Overproduction of sebum can coat the hair and prevent Hairprint from accessing and coloring the roots. The pigment adheres to the sebum on the outside of the hair and then rubs or washes off in a few days.
Overproduction is caused by overactive sebaceous glands (oily skin) or by using shampoos that are too strong, which strip the hair and scalp.
Most shampoos can remove the buildup of sebum, however in order to this they need to be massaged and worked into the scalp, not just the hair. Be sure to wash with warm water, not hot, which can also over stimulate the glands. If you think you have a lot of buildup, we recommend washing your hair with a Clarifying Shampoo on the day of the Hairprint application before you wash with the Pretreatment. Please consult our Hair Residue FAQ for more information.