Similarly, cutaneous (skin) conditions can also involve the mouth and sometimes only the mouth, sparing the skin. The different environmental conditions (saliva, thinner mucosa, trauma from teeth and food), mean that some cutaneous disorders which produce characteristic lesions on the skin produce only non specific lesions in the mouth. The vesicles and bullae of blistering mucocutaneous disorders progress quickly to ulceration in the mouth, because of moisture and trauma from food and teeth. The high bacterial load in the mouth means that ulcers may become secondarily infected. Cytotoxic drugs administered during chemotherapy target cells with fast turnovers such as malignant cells. However, the epithelia of the mouth also has a high turnover rate and makes oral ulceration (mucositis) a common side effect of chemotherapy.