Polydactylous squamous cell carcinoma (SCC) is rare and has been associated with human papillomavirus (HPV). Our recent case was HPV negative and provides evidence for chemical irritants being an alternative cause of subungual SCC. Our patient had spent a number of years with her hands in direct contact with undiluted cleaning chemicals including one containing ethanolamine. Ethanolamine has been shown to have carcinogen sensitizing role. Although HPV has a strong association with subungual SCCs, the accumulation and concentration of noxious substances around and under the nails must also be considered as a potential cause.