Silica supplements, usually from the plant horsetail (Equisetum) can increase the thickness of hair and help it maintain its strength and elasticity. Plant-based forms of silica have varied absorption rates. Choline-stabilised orthosilicic acid has been tested and demonstrated to be effective, but is more expensive.

Silica supplements should be used with caution: horsetail herb can cause liver damage and vitamin B1 deficiency if overused.