Multiple Chemical Sensitivity (MCS) An Overview

[Guest guest]

Multiple Chemical Sensitivity (MCS)

 

(http://www.ei-resource.org/index2.php?option=com_content & task=view & id=134 & pop=1\

& page=0 & Itemid=44)

(http://www.ei-resource.org/index2.php?option=com_content & task=emailform & id=134 & \

itemid=44)

 

_http://www.ei-resource.org/illness-information/environmental-illnesses/multip

le-chemical-sensitivity-(mcs)/_

(http://www.ei-resource.org/illness-information/environmental-illnesses/multiple\

-chemical-sensitivity-(mcs)/)

An Overview

Multiple Chemical Sensitivity is the name given to a syndrome in which a

sufferer experiences multiple _symptoms_ (http://www.ei-resource.org/#) upon

exposure to minute amounts of everyday chemicals. There is currently no

officially recognized definition for Multiple Chemical Sensitivity. This is due

to

the fact that very little is known about it, especially the mechanisms

involved with the onset of symptoms. Leading theories suggest a possible role

for a

hypersensitive central nervous system, immune dysfunction and impaired

detoxification by liver enzymes. Some medical professionals, and even

organizations, continue to insist that the syndrome is psychological in origin,

even in

the face of a growing amount of evidence from studies that show clear

abnormalities in people with _MCS_ (http://www.ei-resource.org/#) on exposure

to

normally safe levels of chemicals. Through 1999 there were a total of 618

scientific articles, editorials, books, book chapters and reports relating to

MCS.

Of these, 308 supported an organic/physiological basis for symptoms whereas

only 137 supported a psychological interpretation. (Source: _www.mcsrr.org_

(http://www.mcsrr.org/) ).

Although there is no definition universally accepted by the established

medical institutions, Multiple Chemical Sensitivity experts (Heuser et al) have

come to a consensus on the criteria for diagnosis, and thus far these criteria

remain unrefuted in the published literature. These criteria are as follows:

 

* The symptoms are reproducible with [repeated chemical] exposure.

* The condition is chronic.

* Low levels of exposure [lower than previously or commonly tolerated]

result in manifestations of the syndrome.

* The symptoms improve or resolve when the incitants are removed.

* Responses occur to multiple chemically unrelated substances.

* Symptoms involve multiple organ systems [Added in 1999].

It's reasonable to expect that these criteria will be officially adopted in

a form very close to the above in the relatively near future.

To complicate matters, however, a number of influential medical

institutions, such as the American Academy of Allergy Asthma and Immunology

(AAAAI), have

renamed the illness as 'Idiopathic Environmental Intolerance' (IEI). They

cite the reason for this to be the fact that no immune system involvement has

been proven thus far and since " sensitivity " in medical jargon technically

refers to an immune reaction, they deem MCS to be inaccurate. For the general

population " sensitivity " and " intolerance " generally mean the same thing and

MCS is so well known that most people are sticking with this name for now.

Symptoms

Many MCS sufferers can trace the start of their illness to an acute exposure

to highly toxic chemicals (Gulf War veterans, and farmers using pesticides

for example). For other sufferers the illness develops over a long period of

time most likely involving chronic low level exposure to chemical substances.

Although MCS can occur on its own, a large number of sufferers also suffer

from CFS, Fibromyalgia and other related disorders. This obviously points to

the possibility that all these illnesses are part of the same underlying

process and likely have common causes.

MCS is a chronic condition with the patient usually experiencing some level

of unwellness all the time. However, patients have an acute reaction when

exposed to minute amounts of the chemicals to which they are sensitive. Often

the level of a chemical that triggers a reaction may be so low that the

sufferer can't even smell it.

Common symptoms of MCS upon exposure:

* Fatigue

* Headaches

* Disorientation

* Dizziness and Faintness

* _Flu_ (http://www.ei-resource.org/#) -like symptoms

* Nausea

* Irregular or Rapid Heartbeat

* Muscle and _Joint Pain_ (http://www.ei-resource.org/#)

* Gastrointestinal problems

* Mood Disturbances - Depression/_Anxiety_

(http://www.ei-resource.org/#) /Irritability

* Short-term Memory Problems

* Asthma/Breathing Problems

* Rashes

Most sufferers have a distinct reaction upon every exposure. It is common to

first experience dizziness, disorientation, rapid heartbeat and mood changes

followed by flu-like illness and muscle/joint aches. In severe cases, the

flu-like illness and aching can persist for days.

Triggers

Reactions in MCS are triggered by a vast array of everyday chemicals from

perfume to diesel exhaust. The common ingredients in most of these chemical

products are hydrocarbon based volatile organic chemicals (VOC's). Phenols

(containing benzene) are commonly implicated. With everyday cosmetic and

household

chemical products, it is generally the addition of perfume that makes them

bad news for MCS sufferers. Typically a sufferer will notice a sensitivity to

one or two things to start with, perfume and cigarette smoke for example, and

then will rapidly become sensitized to more and more chemical sources over a

relatively short period of time. The reasons for this common occurrence are

unknown but it is clearly something that needs to be investigated.

Common chemical triggers in MCS:

Pesticides - When the onset of MCS is a sudden event in an otherwise healthy

person, acute exposure to pesticides is often reported as being the initial

trigger. This is not surprising as these potent chemicals, many of which are

chemically related to war time nerve agents, have multiple negative effects

on the nervous, endocrine and immune systems. By their very nature, they are

designed to exert these effects in order to kill pests. It is naive to think

that these chemicals will not also damage these systems in humans, even in

small amounts. Dr. Sherry Rogers, a respected expert on MCS and environmental

illness, believes pesticides are the no.1 culprit when it comes to chemicals

damaging human health. Common classes of pesticide include the

organophosphates and organochlorides. Organochloride pesticides include DDT,

chlordane,

lindane and dieldrin. Some of the most potent, such as DDT, are now banned in

most western countries but legal pesticides are still very damaging to health.

Pesticides are virtually inescapable, being used on lawns, crop fields,

roadside weed control and even indoors as pest control. Ever stopped to think

what's in flea collars and flea killing products you use on your pets?

Perfume - According to a 1986 report by the Committee on Science &

Technology, U.S. House of Representatives, 95% of chemicals in perfumes and

fragranced

products are synthetic chemicals derived from petroleum. Some of the major

perfume ingredients include benzaldehyde, benzyl acetate, benzyl alcohol,

camphor, ethanol, ethyl acetate, limonene, linalool, a-pinene, g-terpinene and

a-terpineol. All of these chemicals are known to have negative health

consequences, mainly due to effects on the central nervous system.

Gasoline - Vapours cause central nervous system depression. In healthy

individuals, high level exposure leads to symptoms such as eye and respitory

irritation, dizziness, headache, drowsiness and incoordination.

Vehicle Exhaust - Despite attempts in recent years to reduce pollution from

vehicle exhausts, there is no getting away from the fact that burning

petroleum products produces undesirable chemical byproducts. Some of the major

chemicals in vehicle exhaust fumes include carbon monoxide, nitrogen dioxide,

sulphur dioxide, benzene, formaldehyde, polycyclic hydrocarbons and suspended

particles, including PM-10 (particles less than 10 microns in size). Even in

otherwise healthy individuals, these chemicals are known to cause a wide range

of symptoms. In the chemically sensitive, benzene, formaldehyde and

polycyclic hydrocarbons are known to be particularly likely to trigger

symptoms.

Household Cleaning Products - The Environmental Protection Agency (EPA) in

the US states that the air in the average home may be up to 5 times as

polluted as the air outside. Much of this pollution comes from the use of

common

household cleaning products. They also caution that of the many thousands of

chemicals in use only around 3 in 10 have actually been safety tested. Examples

of common chemicals in cleaning products include diethyl phthalate, found in

a range of products, toluene, found in stain removers, and hexane/xylene,

found in aerosol sprays. Diethyl Phthalate is a known endocrine disrupter

(interferes with hormone activity), toluene is a known carcinogen (cancer

causing

agent) and can cause neurological problems, and finally both hexane and

xylene can also damage the nervous system.

Other cleaning products that commonly trigger MCS symptoms include

dishwasher detergent, laundry liquid/powder, fabric softener, air

" fresheners " , and

bathroom/kitchen detergents. Highly fragranced products are always likely to

be the most troublesome.

Personal Care Products & Cosmetics - An equally important contributors to

indoor air pollution are the many personal care and cosmetic products that fill

bathroom cabinets etc. The added danger with many of these, such as hair

spray and deodorant, is that we carry the chemicals around with us all day on

our bodies. Some of the common chemicals found in such products include

cocoamide DEA (detergent in most shampoos, moisturizers and more), propylene

glycol

(in deodorant, shampoos, shaving gels, moisturizers and more), sodium lauryl

sulfate (detergents- in shampoos, toothpastes, more), acetone (nail varnish

remover) and benzaldehyde (hair spray, deodorant, shaving foam, shampoo, bar

soap and more).

Other problem products include shower gels and liquid soaps, nail varnish,

hair styling products, hair conditioners, sun lotion, and scented bath

products. Again the highly fragranced products tend to be the most troublesome

to

the multiple chemical sensitivity patient.

Cigarette Smoke - Often one of the initial symptom triggers when someone

becomes chemically sensitive, probably due to the large amounts of volatile

petrochemicals released into the air, particularly aldehydes. Until recently,

when smoking bans became more widespread, it was very difficult for MCS

sufferers to avoid. Amongst other things, cigarette smoke contains ammonia,

acetaldehyde, acetone, benzene, butyraldehyde, carbon monoxide, formaldehyde,

hydrogen cyanide, nitric oxide and toluene. Ammonia is an irritant to mucous

membranes and can trigger asthma. It also has numerous central nervous system

effects, as do all the hydrocarbon chemicals including the aldehydes, benzene

derivatives and toluene. These hydrocarbons are strongly implicated in most

theories of how MCS occurs, particularly the 'Limbic Sensitization' hypothesis

(see below). Elevated levels of _nitric oxide_ (http://www.ei-resource.org/#)

(NO) are thought to play a major role in chemical sensitivity by a number

of researchers, specifically Dr. Martin Pall, who is himself chemically

sensitive.

Natural gas - Exposure to natural gas will occur at home for most people, if

it is used in heating systems, stoves, water heaters etc. exposure at work

may be common for someone working in industries that involve pulp and paper,

metals, chemicals, petroleum refining, stone, clay, glass, plastic, and food

processing. When burned, natural gas produces hydrocarbon products, primarily

methane, along with carbon dioxide and smaller amounts of carbon monoxide.

New carpet - Most new carpets contain a cocktail of volatile organic

compounds (VOC's) as ingredients in glues, backing materials, flame retardants,

dyes

etc. These include many of the chemicals we are now familiar with, such as

acetone, toluene, xylene, formaldehyde, and benzene derivatives. When the

carpet is new these chemicals " off gas " over a period of around 6 months to 2

years, polluting the air in the home.

Particle board - Manufactured particle board is now used much more widely

than solid wood in our homes, in such things as fitted kitchens, furniture such

as shelving, bookcases, cabinets (especially flat-pack) and laminate

flooring. Particle board is basically wood chip bound together by chemical

adhesives

into solid boards. As with new carpets, new particle board products off gas

VOC's over a relatively long period of time and will trigger symptoms in the

chemically sensitive and may induce sensitivity in previously healthy

individuals. Chemicals that off gas from particle board are similar to those

from

carpets with formaldehyde most often the main offender.

Other common triggers:

The above is by no means an exhaustive list. Here are some other common

triggers of symptoms in MCS patients:

* marker pens

* soft plastics

* new clothes

* new furniture

* newspapers/magazines

* paint

* varnish

* solvents

* glues/adhesives.....and more

In addition to these VOC's that cause a reaction when inhaled, some

sufferers also complain of symptoms when they ingest certain things. These

include:

* Food Additives

* Food Preservatives

* Medications

* Unfiltered Water

The Impact of Multiple Chemical Sensitivity on Quality of Life

Multiple chemical sensitivity is a devastating illness, not just because of

the distress caused by the symptoms themselves, but also from the resulting

effects on all areas of life. An MCS sufferer typically becomes more and more

isolated and withdrawn as they simply can't be around people (wearing

perfume, deodorant etc) or in public spaces where chemicals are routinely used.

MCS

sufferers often lose their jobs as they can't tolerate the chemicals in the

work environment, and relationships often break down as the partner is unable

to understand or adapt to living without the use of common chemical products.

To add insult to injury, because of the current medical confusion over the

illness, patients often have to endure being labeled as attention seekers or

hypochondriacs, as well as having to fight, often in court, to be granted

disability benefits and appropriate housing.

Research Findings

Although the amount of _medical research_ (http://www.ei-resource.org/#)

into MCS is still a lot lower than would be desirable, a relatively high

number of studies have discovered consistent abnormalities in MCS patients and

also been able to show convincing evidence of possible mechanisms in animal and

other laboratory models.

Limbic Sensitization or " Kindling "

One common finding is that a part of the brain known as the 'limbic system',

which has strong connections to the part of the brain involved with our

sense of smell, the olfactory system, shows increased electrical activity in

MCS

patients when exposed to chemicals they are sensitive to. One of the main

functions of the limbic system is the regulation of mood and autonomic nervous

system functions, which would explain why many symptoms of MCS involve

changes in mood, thought and sensory information. As a result of these findings

a

number of researchers have suggested that in MCS, the brain, and limbic system

in particular, has become hypersensitized so that smaller amounts of

chemicals cause the brain to become activated (1 , 2). This theory has been

given a

lot of weight by further research that has shown the limbic systems of

animals exposed to either short term high concentrations of chemicals (such as

formaldehyde), or long term lower concentrations, have become hypersensitized

so

that further exposure to a concentration of chemical, that previously would

have had no effect, now initiates a high amount of electrical activity in

their limbic systems (3 , 4). Researchers found that chemicals that differed

greatly in their structure, had a remarkably similar effect on the limbic

system.

Additionally, the hypothalamus is part of the limbic system and is an

important information processing centre and is the focal point in the brain

where

the immune, autonomic nervous, and endocrine systems interact. It has long

been proposed that a malfunctioning hypothalamus upon exposure to chemical

triggers could produce the symptoms described in MCS through its influence on

all

these body systems. The limbic system is known to be responsive to both

chemical and cortical stimuli. This means that it can be activated either by

thought, or exposure to chemicals in the form of natural neurotransmitters, or

more importantly in the context of multiple chemical sensitivity, in the form

of chemical irritants that enter the body through the nose. This fact provides

a strong argument against those who state that MCS is purely a psychological

illness, as chemicals triggering activation of the limbic system could

initiate mood changes and other symptoms typically labeled as psychiatric.

The sensitization, or loss of tolerance, explanation is the main point

behind the _Toxicant Induced Loss of Tolerance (TILT)_

(http://www.ei-resource.org/toxicant-induced-loss-of-tolerance-(tilt)/) theory

put forward by chemical

sensitivity researcher Dr. Claudia Miller.

Abnormal Regional Cerebral Blood Flow

Another brain abnormality found is abnormal regional cerebral blood flow

(rCBF). In MCS sufferers, blood flow to certain areas of the brain may be

reduced or abnormally chronically, and be further reduced or altered after

exposure

to an offending chemical. This is an interesting finding because reduced

brain blood flow has also been documented in CFS and Fibromyalgia. The link

below shows SPECT brain scans of a woman MCS sufferer before and after exposure

to perfume along with explanation of the results from the lab.

_SPECT Brain scan of MCS sufferer_ (http://www.ourlittleplace.com/spect.html)

 

Porphyria

The porphyrias are a group of rare diseases that occur due to deficiencies

of enzymes used in the process that forms heme. Heme is the important iron

containing protein in blood used in oxygen transport and also in a group of

detoxification enzymes in the liver known as cytochrome P450. Porphyrins are

the

intermediate chemicals in the formation of heme and it is the build up of

porphyrins in different tissues, as well as the loss of ability to detoxify

certain chemicals, that causes the symptoms of the illnesses. The symptoms

present in an individual depend upon which enzymes are deficient and may

include

intolerance's to drugs and chemicals, abdominal and musculoskeletal pain,

photosensitivity resulting in multiple skin problems, fatigue,

neuropsychological

problems, psychiatric problems and pink/purple urine (due to increased

porphyrin content). Porphyrias usually occur in acute episode triggered by

medications, menstrual periods, malnutrition or other illness, at other times

the

sufferer may show no symptoms and normal porphyrin levels. Due to the

similarity of symptoms between these illnesses and MCS, a number of researchers

decided to test MCS patients for increased porphyrin content in urine and stool

samples. One study found that 60-90% of MCS patients tested showed porphyrin

abnormalities. Other findings come from a doctor who had a number of patients

describing pink/purple urine. When tested a significant number had higher than

normal levels in urine and stool samples. The abnormalities however have

been less marked than in the traditional porphyrin illnesses. More research is

definitely needed in this area to further substantiate abnormalities.

Increased Nitric Oxide

Dr. Martin Pall has done a lot of research into levels of nitric oxide and

its derivatives, such as peroxynitrite. Nitric oxide (NO) is a secondary

messenger molecule in the brain, used by cells to communicate. Dr. Pall feels

that there is convincing evidence that elevated levels of NO in MCS patients

brains is a key factor in the illness. He cites the following reasons for this

conclusion:

Several organic solvents thought to be able to induce MCS, formaldehyde,

benzene, carbon tetrachloride and certain organochlorine pesticides all induce

increases in nitric oxide levels.

A sequence of action of organophosphate and carbamate insecticides is

suggested, whereby they may induce MCS by inactivating acetylcholinesterase and

thus produce increased stimulation of muscarinic receptors which are known to

produce increases in nitric oxide.

Evidence for induction of inflammatory cytokines by organic solvents, which

induce the inducible nitric oxide synthase (iNOS). Elevated cytokines are an

integral part of a proposed feedback mechanism of the elevated nitric

oxide/peroxynitrite theory.

Neopterin, a marker of the induction of the iNOS, is reported to be elevated

in MCS.

Increased oxidative stress has been reported in MCS and also antioxidan

therapy may produce improvements in symptoms, as expected if the levels of the

oxidant peroxynitrite are elevated.

In a series of studies of a mouse model of MCS, involving partial kindling

and kindling, both excessive NMDA activity and excessive nitric oxide

synthesis were convincingly shown to be required to produce the characteristic

biological response.

The symptoms exacerbated on chemical exposure are very similar to the

chronic symptoms of CFS (1) and these may be explained by several known

properties

of nitric oxide, peroxynitrite and inflammatory cytokines, each of which have

a role in the proposed mechanism.

These conditions (CFS, MCS, FM and PTSD) are often treated through

intramuscular injections of _vitamin_ (http://www.ei-resource.org/#) B-12 and

B-12 in

the form of hydroxocobalamin is a potent nitric oxide scavenger, both in

vitro and in vivo.

Peroxynitrite is known to induce increased permeabilization of the blood

brain barrier and such increased permeabilization is reported in a rat model of

MCS.

5 types of evidence implicate excessive NMDA activity in MCS, an activity

known to increase nitric oxide and peroxynitrite levels.

Dr. Pall feels that the resulting effects of too much NO in the brain could

result in the symptoms reported by MCS sufferers through various pathways

resulting from overactivation of the brain. He concedes however, that this does

not explain how people become sensitive to chemicals in the first place. For

an explanation for this he postulates that combining his work with elevated

NO, with the limbic sensitization theory, a 'fusion theory' of all aspects of

MCS can be produced.

Read more about this in Dr. Pall's article - _Multiple Chemical Sensitivity -

The End of Controversy_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/mult\

iple-chemical-sensitivity--the-end-of-controversy/

)

 

Other Areas of Research

Immune System

A number of studies have been conducted with MCS sufferers regarding immune

function but the findings have not always been consistent. A couple of

studies have found abnormal T and B-lymphocyte numbers and activity and

increased

autoantibodies, that is antibodies that react with the bodies own tissues.

Some data has shown a low T-helper/Suppressor ratio which would act to impair

immune function. Probably the most consistent finding is that of low natural

killer (NK) cell activity. This is interesting in the light of strong evidence

for low NK activity in _chronic fatigue syndrome_

(http://www.ei-resource.org/illness-information/environmental-illnesses/chronic-\

fatigue-syndrome-cfs-myalg

ic-encephalopathy-me/) and _fibromyalgia_

(http://www.ei-resource.org/illness-information/environmental-illnesses/fibromya\

lgia-(fms)/) . The inconsistent

findings have been suggested to be the result of changes in immune

activation over time following an exposure, with the resulting difficulties in

testing MCS patients appropriately in research studies. How the above findings

would cause the myriad symptoms of MCS is far from clear but immune dysfunction

remains a popular theory for the mechanism of the illness.

For a thorough review of immune system research in MCS, see _Profile of

Patients with Chemical Injury and Sensitivity_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/prof\

ile-of-patients-with-chemical-inju

ry-and-sensitivity/) by Grace Ziem and James McTamney.

Impaired Detoxification/Low Glutathione

Another abnormality in MCS is impaired detoxification of xenobiotic

chemicals (chemicals foreign to the body). It has been found that the ability

to

detoxify these chemicals varies widely in the general population but so far MCS

patients have not been meaningfully studied with regards to this. There are

now a few researchers looking at the metabolism of chemicals in MCS and given

the connection with Porphyria discussed above and the role of detoxification

potential in that group of illnesses, it would seem an area that needs a lot

more attention. It HAS been found however that MCS patients exhibit the lower

than normal levels of glutathione, the bodies major detoxification chemical,

that is also characteristic of _chronic fatigue syndrome_

(http://www.ei-resource.org/illness-information/environmental-illnesses/chronic-\

fatigue-syndrome-c

fs-myalgic-encephalopathy-me/) , _fibromyalgia_

(http://www.ei-resource.org/illness-information/environmental-illnesses/fibromya\

lgia-(fms)/) , _gulf war

syndrome_

(http://www.ei-resource.org/illness-information/environmental-illnesses/gulf-war\

-syndrome/) and _autism_

(http://www.ei-resource.org/illness-information/environmental-illnesses/autism-s\

pectrum-disorders/) . Low glutathione

would result in poor detoxification and excretion of toxic chemicals, leaving

them in the blood stream and tissues where they could cause cellular damage

and interfere with biochemical processes.

For a review of further abnormalities in MCS see _Biomarkers of MCS -

Abnormal Medical Tests and Physical Signs Associated with Multiple Chemical

Sensitivity_ (http://www.mcsrr.org/resources/biomarkers.html)

 

What do we know about common chemicals and health?

The simplest answer to this is...not much.

Since World War 2 the production of synthetic organic chemicals has

skyrocketed. In 1945, total production of these chemicals was under 10 million

tons

compared to 110 million tons today(1).

A total of 4 million chemical compounds were described in the scientific

literature between 1965 and 1989. Of the 60,000 chemicals in wide use in most

western countries in 1989 only around 2% (1200) had been comprehensively

examined by scientists. There is no research data at all available on about

50,000

commonly used chemical substances(2).

A UK academic recently recommended a program to rapidly test and catalogue

30,000 chemicals within the next 5 years. Chemicals found to cause health

problems would then be subjected to more intensive longer term testing. This

would certainly be a step in the right direction.

Related Conditions:

_Electrical Hypersensitivity_

(http://www.ei-resource.org/illness-information/related-conditions/electrical-se\

nsitivity- & -hypersensitivity/) causes

sufferers to develop multiple symptoms when exposed to electromagnetic fields

from

such things as electrical equipment, wiring and power lines. Multiple

chemical sensitivity sufferers may be more likely to also suffer from

electrical

hypersensitivity.

_Sick Building Syndrome_

(http://www.ei-resource.org/illness-information/related-conditions/sick-building\

-syndrome-(sbs)/) involves a group of people

becoming ill whenever they enter a particular building such as an office. Many

factors can contribute to symptoms including both biological and chemical

pollutants.

_References_

(http://www.ei-resource.org/index.php?option=com_content & task=view & id=135 & Itemid\

=45)

Top Multiple Chemical Sensitivity Articles:

_Multiple Chemical Sensitivity: The End of Controversy_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/mult\

iple-chemical-sensi

tivity--the-end-of-controversy/) - Dr. Martin Pall _Perceived Treatment

Efficacy for Conventional and Alternative Therapies Reported by Persons with

MCS_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/perc\

eived-treatment-efficacy-for-conventional-and-alternative-therapies-report

ed-by-persons-with-mcs/) - Dr. Pamela Reed Gibson _Toxicant Induced Loss

of Tolerance: An Emerging Theory of Disease?_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/toxi\

cant-induced-loss-of-tolerance:

-an-emerging-theory-of-disease?/) - Dr. Claudia S. Miller _Objective

Evidence - The Peg upon which all other Issues Hang_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/obje\

ctive-evidence--the-peg-upo

n-which-all-other-issues-hang/) - Don Richard Paladin _Multiple Chemical

Sensitivity: A Literary Critique_

(http://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/mult\

iple-chemical-sensitivity:-a-literary-critiq

ue/) - Patrick Casanova