466 (Sodium carboxymethylcellulose) is a  vegetable gum used as a thickener in foods.

It is an additive to avoid as it is a suspected carcinogen and can cause flatulence, intestinal discomfort and diarrhoea. 

Check the label as it is found in some cordials, flavoured toppings, cereals, snack bars, fruit twists, cakes, soy icecream and instant pasta sauces!  Another reason to eat fresh and unprocessed foods!