Which preservative is commonly used in topical formulations to prevent microbial growth?

• A. Parabens
• B. Glycerin
• C. Propylene glycol
• D. Isopropyl alcohol

Answer: (A)

Preserving topical products to stop microbial growth is essential for safety and shelf life. Parabens are a class of preservatives widely used in creams, lotions, and ointments because they are effective against a broad range of bacteria and fungi and remain stable in typical formulation conditions. They’re used at low concentrations as esters of p-hydroxybenzoic acid (like methylparaben and propylparaben) and are often combined to broaden antimicrobial coverage.

Glycerin and propylene glycol mainly serve as humectants and solvents; they can contribute some antimicrobial effect through high osmotic pressure, but they’re not reliable stand-alone preservatives. Isopropyl alcohol is a strong antiseptic and can inhibit microbes, but it is volatile and can irritate skin, so it isn’t the primary preservative chosen for finished topical products. Hence, parabens are the most common option for preventing microbial growth in topical formulations.