The concern that humectants can draw moisture out applies more to skincare than haircare. The skin is quite thick and has many layers, so a humectant sitting on the surface of the skin (the epidermis) can pull moisture from deeper layers. In haircare, humectants penetrate inside strands right into the medulla (the innermost layer), so they are unable to draw water out of deeper layers since they are already in the deepest one. Using a sealant with a humectant and sealing oil keeps everything sealed in and ensures the humectant remains inside. Humectants present a greater risk in humid climates, as they draw in too much water and cause the cuticle to swell and become damaged.