Indigo carmine with E-number 132 is a synthetic, water-soluble dye that is not absorbed by the body's cells. It is also called Indigotine and Blue no. 2. In particularly sensitive persons, however, the substance may cause allergy-like symptoms. Its color is blue or yellow depending on the pH of the preparation. Indigo carmine is approved as a dye in soft drinks and a variety of foods.
The allowable amount is 5 mg / kg body weight. The light blue glucosamine tablet marketed by Pharma Nord in the UK contains less than 1/10 mg of the dye.
A lake pigment is an organic pigment unlike pigments from minerals which are inorganic. A lake pigment is manufactured by precipitating the dye with an inert (unreactive) 'mordant' - usually a metallic salt.