Everyone has a hydrolipidic film on their scalps, this fatty layer protects the skin and hair follicles from the environment (think UV rays and pollution), it also helps to keep hydration levels optimal. But some people have too much of this hydrolipidic layer. Why? Well, the causes are annoyingly varied. First up, there are external causes that can trigger an overproduction of this hydrolipidic layer. Those include heat tools, hard water, exercise and pollution. Second are the internal factors such as stress and exhaustion, an unhealthy diet, genetics and periods. Work through these factors and ask yourself which of these could be contributing to your greasy roots?