Aspergillus niger is a type of black mold and known allergen. While the chemical produced during the fermentation process is identical to the one naturally occurring in citrus, concerns have been raised over whether there could be trace amounts of mold residue present in the citric acid used in commercial applications. Because this manufactured form of citric acid was used prior to the Food Additives Amendment in 1958, it was excluded in safety evaluation and granted GRAS status due to lack of demonstrated harm. While no well-performed studies have been conducted showing any adverse effects of citric acid, some case studies have evaluated potentially negative health implications from mold exposure due to manufactured citric acid intake. Higher quality research is warranted and caution should be used with this ingredient as it is widely used in many goods. Pfizer has been producing citric acid since 1919.