Silica, commonly found in the form of silicon dioxide, is often included in supplements marketed for hair health. The scientific evidence supporting silica's role in promoting hair growth or improving hair strength is limited but not entirely absent. Some small-scale clinical studies and animal research suggest that silicon, particularly in the form of orthosilicic acid, may play a role in the synthesis of collagen and glycosaminoglycans, which are structural components of hair, skin, and nails. For example, a 2007 randomized controlled trial found that supplementation with choline-stabilized orthosilicic acid improved hair tensile strength and reduced brittleness in women with fine hair, though the sample size was small and the results have not been widely replicated.

Mechanistically, silicon is thought to contribute to the formation of connective tissue and may support the integrity of the hair shaft. However, comprehensive reviews and larger trials are lacking, and the overall quality of the evidence remains low. Most claims regarding silica for hair are based on its theoretical role in connective tissue health rather than robust clinical data. Therefore, while there is a plausible scientific rationale and some preliminary evidence, silica’s use for hair health is not strongly validated by high-quality research.