“Silica ingested orally is essentially nontoxic, with an LD50 of 5000 mg/kg (5 g/kg).[6] On the other hand, inhaling finely divided crystalline silica dust can lead to silicosis, bronchitis, or cancer, as the dust becomes lodged in the lungs and continuously irritates them, reducing lung capacities.[27] Studies of workers with exposure to crystalline silica have shown 10-fold higher than expected rates of lupus and other systemic autoimmune diseases compared to expected rates in the general population.[28]” (from Wikipedia entry)
rmsbeautyblog 
How about your own silica “un” powder?
“Silica ingested orally is essentially nontoxic, with an LD50 of 5000 mg/kg (5 g/kg).[6] On the other hand, inhaling finely divided crystalline silica dust can lead to silicosis, bronchitis, or cancer, as the dust becomes lodged in the lungs and continuously irritates them, reducing lung capacities.[27] Studies of workers with exposure to crystalline silica have shown 10-fold higher than expected rates of lupus and other systemic autoimmune diseases compared to expected rates in the general population.[28]” (from Wikipedia entry)
Hi Mara,
This is an excellent question! To read more about this please click here