Both CB1 and CB2 receptors are found in the human skin, on keratinocytes, sebaceous glands, hair follicles, and melanocytes. Activation of CB1 on hair follicle cells slows hair growth. Cb2 activation on sebaceous glands increases lipid production, important for maintaining healthy hair and skin cells, but overproduction could lead to conditions such as acne. As in other parts of the body, regulation of the immune system is another important function of the ECS in the skin where it generally plays an anti-inflammatory role. CB1, CB2, and TRPV receptors are all also involved in sensations of pain and itch. CB1 knockout mice have been shown to have impaired development and differentiation of keratinocytes and were slower to repair impermeability, which is seen in the skin disease eczema. The combined effects of CB1 and CB2 are needed to prevent excessive allergic immune response in the skin, and increasing endocannabinoids had a beneficial effect on dermatitis in experimental models. Dysfunction of the endocannabinoid system may also play a role in other inflammatory skin diseases such as psoriasis, contact dermatitis, and other forms of dermatitis.