Itaconic acid is a dicarboxylic acid that is methacrylic acid in which one of the methyl hydrogens is substituted by a carboxylic acid group. It has a role as a fungal metabolite and a human metabolite. It is a dicarboxylic fatty acid, a dicarboxylic acid and an olefinic compound. It is functionally related to a succinic acid. It is a conjugate acid of an itaconate(2-). Itaconic acid (IA) is an unsaturated dicarbonic organic acid. It can easily be incorporated into polymers and may serve as a substitute for petrochemical-based acrylic or methacrylic acid. It is used at 1–5% as a comonomer in resins and also in the manufacture of synthetic fibres, in coatings, adhesives, thickeners and binders.