When food are manufactured, chemicals are put in them. These chemicals are called food additives.
They are added for a number of reasons:
Preservatives---to keep the food fresh.
Flavourings---to replace the flavour of the food that is often lost when it is processed.
Colourings---to make the food look more attractive and appetising.
Food additives are harmful. Some may cause asthma and headaches, some cause over-activity in children, some even can destroy vitamins.