Silica, also known as silicon dioxide, is a trace element that is a combination of silicon and oxygen.  It is a naturally occurring element in many plants and whole grains.  Silica promotes the production of collagen, so while it does not promote hair growth, it does strengthen hair and prevent hair thinning by creating a strong network within the scalp. Silica is important for optimal collagen synthesis and activation of hydroxylating enzymes that improve the strength and elasticity of the scalp.