Silica does exist in the blood. Silica, in the form of silicon dioxide (SiO2), is naturally present in trace amounts in the body and can be found in various tissues and fluids, including the blood. Warning signs of silica deficiency include brittle nails, longitudinal ridges on the nails, poor hair growth and breakage, hair loss, premature wrinkles, osteoporosis, poor muscle tone, cellulite, and stretch marks, especially following pregnancy, brittle teeth, dental caries, acne, eczema, boils, sca