An environmental illness is a set of symptoms or a disease caused by chemicals, fumes, pollution, allergens, viruses, or toxins or physical hazards found in the environment. Exposure to toxic chemicals or other hazards may occur in the home, workplace, or community.

The symptoms of an environmental illness depend on what is causing it. The symptoms may be like those caused by other illnesses. Examples are headache, cough, fatigue, and nausea. And symptoms may vary according to the amount and type of exposure. Environmental illnesses may be difficult to diagnose. And they are sometimes mistaken for other illnesses.

Symptoms may occur suddenly and disappear when exposure to the substance ends. For example, headaches or grogginess caused by carbon monoxide at home can go away when the people who live there go to work or school. Sometimes symptoms may not develop for years, which can occur after exposure to cancer-causing chemicals.

The first treatment for an environmental illness includes getting rid of or reducing exposure to the things causing the illness. Additional treatment is based on the specific symptoms and part of the body that is affected.