During the last century countless completely new chemicals have been introduced to the environment, and if not obviously harmful it may be many years before it is recognised that a specific chemical can cause illness. MSC has vague symptoms similar to Gulf War syndrome, or to ME, and although all these illnesses have been declared as to be "all in the mind" there is now increasing evidence to the contrary, and there is a great deal of controversy.

An example is when gross exposure to a toxic chemical, as when a pipe bursts, produces acute symptoms which subside, but is followed by reacting to mere traces of the chemical, and also gradual acquisition of multiple sensitivity to the many other chemicals encountered in everyday life, such as scent, alcohol, formaldehyde, artificial fragrances and insecticides etc.

More commonly there is no acute exposure episode, but long term exposure at work, or in the home to very toxic chemicals sued to eradicate dry rot. People find that they begin gradually with wheezing or other symptoms to many household chemicals, so that avoidance becomes a great problem, and in extreme cases where the patient seems to be "allergic to everything" attract press publicity. There are no laboratory tests which will give a reliable diagnosis, the symptoms are all subjective, and the patients are often dismissed as either malingerers or neurotics, often leading to resentment and emotional upset as a result of being disbelieved. This is a condition waiting for a test to establish it as a definite entity, as it is only in case of industrial exposure to the isocyantes and phthalates the specific IgE can be demonstrated in the blood.

It is obvious that deliberate exposure to the suspected chemicals in tiny amounts in a closed chamber, given precisely and using a double blind protocol to reproduce the symptoms, might convince the medical profession that this is a real illness. Unfortunately there are many difficulties in carrying out such investigations, which could make the patient quite ill, and the technology has not been properly developed.

To start with the suspected chemical would be introduced into the chamber in a concentration well below the level which might cause harm, then given in increasing amounts until the patient reacts, or it is evident that no reaction is going to take place. As patients may be sensitised to many chemicals, they might need to be challenged with several on different days, or perhaps the subject might need to be challenged with several on different days, or perhaps the subject might react only when they are all present the subject might react only when they are present, as they might be having an additive effect.

Before this type of test could be carried out it would be preferable if prior to the tests the sufferer was isolated in a special hospital where all the usual chemicals and pollution are rigidly excluded. Unfortunately there is only one unit in this country offering such isolation facilities, there are none on the NHS, and very few specialists with an interest in environmental illness.

At this time treatment depends on mainly identifying and avoiding chemicals which cause symptoms, which is not always easy or practical. In cases where compensation is sought for industrial or accidental exposure the lack of reliable laboratory tests for chemicals puts the plaintiff at a serious disadvantage.

Dr Harry Morrow-Brown