Work and environmental exposures can lead to or worsen several different types of common diseases, for instance asthma, dermatitis, hepatitis B, carpal tunnel syndrome, and cancer. In a number of cases, the environment or work-related illnesses do not show distinctive clinical presentations: asthma resulting from a cat allergy does not differ from asthma caused by latex allergy; median nerve entrapment associated with repetitive motions has the same set of signs and symptoms as carpal tunnel syndrome arising due to pregnancy; headache caused by inhalation of carbon monoxide can be diagnosed as severe headache or migraine. Symptoms associated with hazardous exposures can be similar to normal complaints involving any body system and other common medical diseases. There are certain exposures that can lead to immediate or subacute symptoms (for instance acute chemical reaction and allergic reactions), whereas others can result in more delayed outcomes (for example pneumoconiosis and cancer). The differentiating feature is the association to an occupational or environmental exposure. The history of occupational and environmental exposures can play a significant role in the identification, treatment, and prevention of occupational/environmental injuries and illnesses.