Michael Braungart, a German chemist and the scientific director of environmental nonprofit Hamburg Environmental Institute, carried out tests on face masks that people had worn shortly before developing rashes on the face.
He detected formaldehyde, aniline and other toxic chemicals in the used masks.
Formaldehyde is used to give new face masks a "clean" smell. It is classified as a carcinogen by the World Health Organization's (WHO) International Agency for Research on Cancer. Inhaling formaldehyde over a short period of time can cause burning sensations in the eyes, nose and throat, as well as coughing, wheezing and nausea.
Aniline, a highly corrosive industrial chemical, is also a known carcinogen. Additionally, it is considered a pollutant of serious concern due to its high toxicity.