In an open study, women with biologically aged skin and fragile or thin hair, or brittle nails were treated orally with 10 ml colloidal silicic acid (Silicol) once daily for 90 days and applied colloidal silicic acid to the face for 10 min twice daily. Of the 50 subjects treated, three withdrew from treatment after 30 days because of excessive drying of the facial skin due to topical application. In the remaining 47 subjects there was statistically significant improvement in the thickness and turgor of the skin, wrinkles and condition of the hair and nails. The number of mottles also declined, but the change was not statistically significant. Ultrasound measurements did not detect any statistically significant change in the thickness of the epidermis or elasticity of the skin, but there was a significant increase in the thickness of the dermis.