Multiple chemical sensitivity (MCS), also known as idiopathic environmental intolerance (IEI), is common in people with fibromyalgia (FMS) and chronic fatigue syndrome (ME/CFS). Some researchers believe they are all part of a family of illnesses, which some have called "functional somatic syndromes" or "environmental illness." A term now gaining prominence is "central sensitivity syndromes."
In central sensitivity syndromes, the central nervous system becomes hyper-responsive to certain stimuli. Those stimuli can include pain, temperature, light, and, especially in the case of MCS, chemicals.
What is Multiple Chemical Sensitivity?
MCS has been recognized for a couple of decades, but it's still a fairly controversial diagnosis. It's also an illness that's gone through multiple names. Along with environmental illness, it's been called chemical injury or chemical sensitivity. Currently, most people know it as MCS, but doctors often call it idiopathic environmental intolerance.
Someone with MCS has negative reactions to even small amounts of chemical substances in their environment. While chemicals can make just about anyone sick if they're at high-enough levels, in MCS, even low amounts lead to symptoms.
Common problem substances include:
- Fragrances, such as in cleaning products, perfumes, candles, and hygiene products
- Cigarette smoke
- Paint fumes
- Gasoline fumes
- Industrial chemicals
- Chemicals in tap water
Some of these things trigger symptoms with their smells or upon physical contact, while others must be ingested.
Not everyone with MCS is sensitive to the same things: one person may be unable to be in the room with someone smoking or wearing scented lotion, but be fine at the gas station; meanwhile, someone else can handle hygiene-product fragrances but gets sick around pesticides and cleaning products. Someone else may have problems with all of those things.
What Causes MCS?
The causes of MCS are still unclear. Some cases seem to start after a chemical injury resulting from high-level exposure; however, this can't explain all cases.
We also don't understand the exact mechanism by which chemicals trigger symptoms. Researchers are looking in several directions, including:
- Chemical impact on the brain and nervous system,
- Immune system reactions,
- How sensitivity to one chemical may "cross over" to other chemicals.
Symptoms of MCS
Symptoms of MCS can range from mild to severe. They vary from person to person, but many of the common symptoms are:
- Extreme fatigue
- Stinging eyes
- Wheezing or breathlessness
- Runny nose and other sinus problems
- Sore throat and cough
- Impaired concentration or memory
- Muscle and joint pain
- Digestive problems
- Difficulty sleeping
Other than the stinging eyes, wheezing, and runny nose, these symptoms look a lot like those of FMS and ME/CFS, making it difficult to figure out where your symptoms are coming from.
For a doctor to diagnose you with MCS, you have to meet several criteria:
- Symptoms must be reproducible (meaning they're triggered by each exposure to a particular substance);
- It must be a chronic (long-lasting) problem;
- The symptoms must improve or resolve completely when the problem substances are eliminated;
- Symptoms are the same whether the exposure is to a small amount or a large amount;
- For the "multiple" aspect, symptoms must occur when in contact with unrelated substances;
- Symptoms must involve more than one organ or area of the body.
Some research is showing possible physiological abnormalities in people with MCS, but thus far the science isn't strong enough to have led to a diagnostic test. Much more work needs to be done to give us a solid understanding of what's going on in people with this condition.
Treating & Managing MCS
We don't have any drugs or medical treatments for MCS in general. However, some people may have success with treatments aimed at specific sensitivities.
The primary way to manage MCS is to avoid the things that make you sick. Depending on what those things are, that can be extremely difficult. If you're sensitive to chemicals used in your job, you may need to consider a different field. If you're bothered by scented hygiene products, it may become difficult to be in large groups of people. You may need to remove items from you home and will likely need to be very careful what you buy.
Research suggests that reducing your stress, especially via techniques of mindfulness-based stress reduction, may help symptoms of MCS, along with FMS, ME/CFS, and several other common overlapping conditions.
Some doctors say they've seen patients improve by making positive nutritional changes or improving their immune systems, but these have not been consistently effective for everyone.
MCS in FMS & ME/CFS
If you already have one of these conditions, it can be hard to figure out whether you have the others, because symptoms can be so similar. They key is to watch for changes, such as new symptom clusters (i.e., headaches and nausea that occur together) or symptom triggers (such as fragrances, stress, or exertion). Once you become aware of changes, be sure to talk to your doctor about them, and emphasize that they are new. It may help to keep a symptom journal.
Research suggests that having more than one of these illnesses has a bigger impact on your overall well-being, symptom load, and quality of life. It's important for you to get all of your conditions accurately diagnosed so that you can treat and manage each one.
Some strategies will do double (or triple) duty, though. Good nutrition and a healthy immune system may improve all of your illnesses, as well as your general health. Avoiding symptom triggers is good advice for all these illnesses as well.
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