It’s a really soft plastic, so it lasts a long time. That being said, it should be kept clean, and rinsed thoroughly after each use to prevent bacteria growth.

Give a shampoo wash, and massage it on his scalp with your fingers for about a minute. After that, let the shampoo sit for about two or three minutes, and then start taking the brush/comb through his hair back-and-forth just over and over again for about three minutes. You will see an improvement in less then a week.