What is MCS?

Multiple Chemical Sensitivity (MCS) is a term used to name the experience of being chemically sensitive to multiple substances and having mild to severe and/or life-threatening reactions to those substances.

Individuals who have sensitivities to multiple chemicals are suffering from an Environmental Illness (EI).

“Environmental Illness” or “EI” is an overarching term that is used to describe the illnesses and diseases that some people have whose symptoms and reactions occur or worsen when they are exposed to chemicals or substances in the environment (the external environment, on other people, and on themselves.)

In an EI, something in the environment is toxic and/or an irritant or incitant and can cause individuals to have mild to severe and life-threatening reactions from their exposure to the chemical or substance.

Current research (see T.C. Theoharides, MD, here and here) has shown that the reactions to the triggers individuals with chemical sensitivities experience have their basis in mast cell function and in mast cell degranulation. Click/Tap here to learn more about mast cells.

Is it a mental illness?

Experiencing mulitple chemical sensitivities is not a mental illness. It is a real, physiological illness not psychological. The effects of chemical sensitivities on a person and on their life can be devastating. People do not always know or realize that what they are experiencing has a name. Most physicians are not trained to recognize, diagnose, or treat chemical sensitivities and environmental illnesses. Many healthcare professionals deny they exist.

What can someone do to not become worse?

People with sensitivities to multiple chemicals must avoid and minimize their exposures to the chemicals and environments that cause them to have what can often be severe and potentially life-threatening reactions. Individuals with chemical sensitivities may need to avoid small and large groups of people, public places (like libraries, buses, trains, offices, parks, restaurants,) car exhaust, certain foods, cell phones, soaps and detergents, electrical currents, plastics—and this is not a complete list of all the triggers. Chemical sensitivities can be permanently disabling for some while others are able to continue working once reasonable accommodations are in place.

I don’t understand about triggers.

The word ‘trigger’ refers to whatever chemical or substance it is that makes a person with chemical sensitivities have a reaction. The specific triggers that cause a reaction, as well as the reactions themselves, can be different for different people.

Many times individuals who have chemical sensitivities will wear face masks with activated charcoal filters to decrease their exposure to the chemicals in the environment. It is important to remember that in order to receive medical care, a person with chemical sensitivities must intentionally put themselves into an environment, (the doctor’s office, hospital, clinic, health center, private practice office,) that has the potential to cause them permanent, irreversible harm and damage while making them very, very ill with their reactions in the process.

What do I do?

If you feel that you may have MCS or an EI, contact a physician to receive medical help. The information presented here is not medical advice and is in no way a substitute for receiving medical advice and treatment from a doctor.


Learn More:

About MCS & EI




Toxins in our Lives














Education & Training


The Counseling Center at CELA is not endorsing any of the above links or their content and is providing these links as informational resources only.