Multiple Chemical Sensitivity or Multi-Sensory Sensitivity?
MCS and MSS - What is It?
Multiple chemical sensitivity (MCS) is a situation in which multiple symptoms reportedly occur with low-level chemical exposure. There are several theories explaining the cause of MCS, including allergy, toxic effects and neuro-biologic sensitization.
Multi-Sensory Sensitivity is heightened sensitivity towards routine sensations like light, sound, smell, and touch. The sensory amplification, or the tendency to perceive normal daily external or internal bodily sensations as being particularly unpleasant or bothersome is the basis of MSS.
Though unrelated, the causes and symptoms of both these conditions can be studied in unison. People with Multiple Chemical Sensitivity (MCS) are hypersensitive to chemicals they absorb through their skin (such as cosmetics), inhale (such as perfume), and ingest (such as alcohol and medications). The majority of MCS cases also meet diagnostic criteria for chronic fatigue syndrome and/or fibromyalgia.
Less commonly recognized is the extensive overlap of MCS with multi-sensory sensitivity, also known as MUSES syndrome. People with MUSES are not just hypersensitive to chemicals but also to all or most other types of sensory stimuli, including bright sunlight, loud noise, hot weather, light touch on their skin (shirt tags bother their neck), and spicy foods (they eat blander food than before their illness).
Some patients even notice increased sensitivity to vibration when near moving trucks or trains and increased sensitivity to electromagnetic fields when near-desktop computers.
So far, the only known cause of MUSES syndrome is carbon monoxide poisoning, which has a long-lasting effect on sensory nerves.
The Good and the Bad News for People with MUSES
Let’s tackle the bad news first.
The bad news for people with MUSES is that they suffer more than people with pure MCS, whose symptoms are triggered only by chemical exposures and at most one or two other types of sensory stimuli. The good news for people with MUSES, however, is that, unlike MCS, their illness is associated with an easily testable, treatable, and curable oxygen deficiency.
Blood Oxygen testing of arterial and venous samples (taken from the same elbow without a tourniquet) shows that the arterial level of oxygen going into their body is normal but that too much oxygen remains in their veins. This proves that people with MUSES are having trouble absorbing oxygen from their blood into their tissues, resulting in low oxygen consumption or tissue hypoxia.
The most important blood gas measures to consider are the artero-venous (a-v) difference in the partial pressure of oxygen (PO2), which is abnormal if less than 55mmHg, and the a-v difference in oxygen saturation (O2Sat), which is abnormal if less than 30mmHg.
Consistent with low oxygen consumption, people with MUSES usually also have lower than normal carbon dioxide output (PvCO2-PaCO2 less than 7mmHg), showing impaired oxidative metabolism.
Other symptoms associated with tissue hypoxia include frequent headaches, shortness of breath, depression, anxiety, chronic fatigue, and fibromyalgia-like muscle pain.
Fortunately, these and other symptoms of multi-sensory sensitivity--including chemical sensitivity--respond well to supplemental oxygen, which is the standard treatment for tissue hypoxia. (Note that the use of oxygen for any medical purpose requires a prescription from a physician.)
People with MUSES who take supplemental oxygen at home for just two hours per day should begin to notice some improvement within a week. Three to four months of daily treatment are usually needed, however, before they are able to stop taking the oxygen without their symptoms returning. Unfortunately, this therapy does not help people with pure MCS who do not have tissue hypoxia.
For more information, see "What you need to know about carbon monoxide poisoning" or call MCS Referral & Resources at 410-889-6666.