Employees working in the manufacturing and processing of leather are exposed to a variety of skin irritants and contact allergens. In the first processing steps, alkaline leaches and acids are being used. Tanning is mostly done using chromium salts. To avoid mold infestation, leather is treated with various biocides. Usually, leather is retanned with vegetable and synthetic tanning agents, formaldehyde and glutaraldehyde, amino resins, and polyacrylate or polymethacrylate solutions. Most leather dyed using azo dyes or metal complex dyes.