4-Hydroxybenzoic acid

4-Hydroxybenzoic acid (CAS 99-96-7) is an aromatic organic acid also known as p-Carboxyphenol, 4-Carboxyphenol, and by trade references FEMA 3986 and NSC 4961. It serves as the parent compound from which paraben esters are synthesised, making it a key intermediate in preservative chemistry. No E-code is assigned to the free acid form.

In cosmetic formulations, it functions as a direct antimicrobial agent by disrupting microbial cell membrane integrity, and acts as a UV stabiliser by absorbing radiation in the 270–300 nm range to protect sensitive active ingredients. In pharmaceutical manufacturing, it is used as a precursor in the synthesis of methylparaben and propylparaben, both Ph.Eur.-listed preservatives.

The material is supplied as a crystalline powder meeting Ph.Eur. and FCC specifications, with pharmaceutical and food-grade options available. It is registered under REACH and classified under HS code 29182930. Packaging typically ranges from 25 kg fibre drums to bulk quantities on request.