They may have what appears to be a minor allergy to one or more chemicals. Other people are much more seriously affected. They may feel tired all the time, and suffer from mental confusion, breathing problems, sore muscles, and a weakened immune system. MCS is a disorder triggered by exposures to chemicals in the environment. Individuals with MCS can have symptoms from chemical exposures at concentrations far below the levels tolerated by most people.
Symptoms occur in more than one organ system in the body, such as the nervous system and the lungs.
Exposure may be from the air, from food or water, or through skin contact. The symptoms may look like an allergy because they tend to go with exposures, though some people's reactions may be delayed. As MCS gets worse, reactions become more severe and increasingly chronic, often affecting more bodily functions. No single widely available medical test can explain symptoms. In the early stages of MCS, repeat exposure to the substance or substances that caused the initial health effects provokes a reaction.