How dangerous is silica gel to children?

Researched by Shaikh Ubaid TorontoAnnie, Edinburgh

• Alone, silica gel is non-toxic, non-flammable and chemically unreactive. However, some of the beads may be doped with a moisture indicator, such as cobalt (II) chloride, which is carcinogenic. Cobalt (II) chloride is deep blue when dry (anhydrous) and pink when moist (hydrated). This is the reason most silica gel packets are labeled as dangerous or poisonous when eaten. Crystalline silica dust can cause silicosis but synthetic amorphous silica, which is what silica gel is, does not cause silicosis. A chemically similar substance with far greater porosity is aerogel. Rich Paddon, Manchester, UK

• Presumably you dehydrate, but by how much is determined by what quantity you eat. Jenny, Woking, UK

• Not a lot, apparently. According to the advice of the Utah Poison Control Centre, "Silica gel is a desiccant which absorbs moisture and is included in the packaging of many products such as shoes, purses, medications, electronic equipment, computers, etc. Desiccants are the most common foreign object ingestion by children under 6 years of age reported to the Utah Poison Control Center, with 584 reports in 1999. Silica gel packets are printed with very strong Words of caution - DO NOT EAT, HARMFUL IF SWALLOWED, THROW AWAY. Parents may panic after reading the silica gel caution label, if their child puts the package in their mouth or eats the product. Rest assured, the contents of the packet, silica gel, is basically sand and it is not harmful if swallowed. However, caution should be taken to keep the product out of small children's reach, because the silica gel packet may be a choking hazard." Roger Greenhalgh, Newport, Shropshire U