Preservatives are those chemicals which used alone or in combination to prevent the growth of microorganisms in solution. Preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes. Some examples of Preservatives: Sodium benzoate, Potassium sorbate, Methyl hydroxybenzoate (methylparaben), Benzoic acid, Chlorobutanol, Sorbic acid etc. Some preservatives are used in pharmaceutical emulsion to maintain products availability and activity.