이 원료는 3급 부틸기로 치환된 4-메톡시페놀 이성질체의 혼합물이며 주로 3-t-부틸-4-하이드록시아니솔과 그보다 적은 양의 2-t-부틸-4-하이드록시아니솔로 구성된다.

Tert-butyl-4-methoxyphenol: BHA (butylated hydroxyanisole) is a preservative and stabilizer; U.S. National Toxicology Program, a part of the National Institutes of Health, has classified BHA as "reasonably anticipated to be a human carcinogen" based on evidence of carcinogenicity in experimental animals.

本品は、４－メトキシフェノールに <I>t</I>－ブチル基が置換したものの混合物である。主に３－<I>ｔ</I>－ブチル－４－ヒドロキシアニソールからなり、少量の２－<I>t</I>－ブチル－４－ヒドロキシアニソールを含み、次の化学式で表される。