Usually, the bristles of scalp massager brushes are made of silicone, plastic, and rubber. The plastic ones are cheaper and tend to be sharper. So, they may scratch and damage the hair and scalp. On the other hand, the rubber tips are also hard but not like those of plastic ones. Of all, silicone bristles are usually triangular in shape, soft, and heat-resistant. So, they are safe to use for men, women, and kids.