A Broad Introduction
Rhinitis & Hay Fever
Children & Infants
Allergy to Animals
Some environmental contaminants, such as mercury, lead, and arsenic,
are very toxic and the symptoms of poisoning can be very insidious
in onset, but this is not allergy, which is an excessive reaction to
a very tiny amount of the allergen. Our homes are increasingly
contaminated with chemicals, but to condemn all chemicals relatively
new to our environment would be just as foolish as to accept them
all as harmless. In my experience very few patients can be clearly
shown to react to environmental chemicals, so it is difficult to
know whether the case-histories shown here are exceptional, or if
there are many others where the association has not been recognised.
Are these cases the tip of an invisible iceberg? Are less extreme
Some chemicals are more liable to cause allergies than others, just
as mites, pets, and pollen are the commonest natural substances to
cause allergic problems, so it is important to know which chemicals
are most allergenic and where they are to be found. For example
modern furniture is often made with a mixture of sawdust and
formaldehyde resin glues, which liberate traces of formaldehyde into
the air for a long time after they are installed in the home. This
produces the characteristic odour of new furniture and carpet shops
which have an immediate effect on many people, but it is unclear how
important this can be except to a few very sensitive subjects.
Many houses have had urea-formaldehyde foam, which is banned in
Canada, installed as cavity wall insulation.
In recent years there has been a great deal of scattered research on
a group of chemicals called isocyanates, which very allergenic and
used the manufacture of many plastics, especially polyurethane foams
which are used everywhere in the modern environment. Many workers
exposed to isocyanates developed occupational asthma. Recovery on
removal from exposure was expected, but asthma quite often continued
unabated. Much evidence relating to isocyanates and allergy has
recently been reviewed, and has been pointed out that most homes
today contain polyurethane foam products, such as mattresses,
pillows, and cushions, so some exposure will continue in the home
and could explain persistence of asthma.
All these ubiquitous plastic products,
which have only been introduced within the last fifty years, still
contain traces of isocyanates left over from the manufacture of the
polyurethane foam, so that our homes have become contaminated to a
varying degree with these very potent sensitisers. The increase in
use of these products in bedding has been found to increase in
parallel with the increase in asthma in children in one study, and
the increase in usage of this bedding material also corresponds to
the development of asthma in ethnic minorities who adopt a western
life-style. Isocyanates are the largest cause of occupational asthma
and their greatest use is in the production of polyurethane foams
during which there is usually an excess of isocyanate which is not
totally used up during the chemical reaction which takes place
This significance of this observation will have to await further
research, but it has also been shown that sensitisation can be
caused by absorption through the skin as well as by inhalation.
Evidence for absorption of allergens by this route has been clearly
associated with the causation of peanut allergy from ointments
rubbed into babies skins which contain peanut oil, often called
arachis oil on the label. The development of dangerous allergies to
latex over recent decades could be attributable to increased use of rubber
gloves, and the simultaneous use of hand disinfectants which may
damage the skin and facilitate the entry of latex allergens through
Natural Gas and Allergy to the Added Smells
Surveys have shown that cooking by gas causes increased pollution
with nitrous fumes in the kitchen, especially without an extraction
fan, and increases incidence of asthma. This patient insisted that
gas was the cause of her chronic asthma, and even that she could
tell within minutes if a strange house had natural gas or not, even
when the central heating was off, by her chest tightening up, but
the possibility was dismissed as impossible.
Because natural gas has no smell it is necessary to add smells as a
safety measure, so the Gas Company supplies ‘scratch’ cards which
contain micro-encapsulated substances which, when scratched,
liberate the smells which are added to gas so that householders will
know what gas smells like. This patient reacted to only one, her
peak flow dropping from 400 to 250 by three hours, so that she was
reluctant to try this again.Further confirmation was obtained by
making a 10% mixture of natural gas and air in a rebreathing bag and
showing that this also produced a drop in the peak flow.
This case was obvious and easily confirmed, but how many similar
cases exist where the patient is less observant, and chronic asthma
caused by gas? Supplementary evidence was dramatic improvement on
holidays, which could have been due to other environmental
possibilities. In this case some confusion was caused by the fact
that every time she went to the local pub with her husband she got
asthma, which could have been triggered by smoke pollution or
central heating. She did not like alcohol and always had orange
juice, which she never took at any other time. Orange juice was
proved to be the cause of the asthma, and if she drank apple juice
nothing happened when at the pub.
Air ‘Fresheners’ can Cause Asthma
One afternoon I saw a 46 year old man with asthma so severe that I
admitted him direct from out-patients. On my rounds the next morning
I was surprised to find that he had made a complete recovery
overnight with remarkably little treatment. His story was had had
asthma for several years, and lived with his sister who had such an
obsession with smells that there were air “fresheners” all over the
I obtained a “freshener” and arranged for it to be secreted under
the mattress without his knowledge on two occasions. The result each
time was severe asthma by the morning, peak flow dropping from 450
to 300 l/min.
I then got in touch with the makers who supplied samples of the
three “fragrances “, and by exposing him to each in turn
established that only one of the three was responsible for his
asthma, as shown by the peak flow readings after exposure.
Unfortunately the makers refused to disclose the nature of these
“fragrances”, but after all the fresheners were thrown out he had no
more asthma. How many other asthmatics are caused, as in this case,
or aggravated by these unnecessary “fresheners”?
Insecticides can cause allergies
Insecticides can rarely be proved to cause allergic problems,
although this is not unlikely as they are found everywhere in the
environment. Unfortunately there are no pictures, so we only have
her word for it, but this middle-aged lady who bought a new caravan
is the most convincing.
She and developed gross swellings on one or
other side of the face on holiday for which she blamed the new
caravan, but eventually noticed that the swelling of the face was
related to the proximity of a block of insecticide she had hung near
her cooking stove.
If she hung it on her left the left side of the
face swelled up, and on the right the right swelled up, so even a
few feet away there were enough molecules of insecticide to cause
The significance of this sort of anecdote is very
difficult to assess, but less extreme examples probably do occur
without being recognised. Unfortunately she was unwilling to undergo
a re-exposure so that photographic evidence could to be obtained.
Washing Powder Asthma
Another lady had had a poor sense of smell and chronic asthma for
several years. The only clue was that she felt wheezy every time she
was near the washing powders in the supermarket, even when in a
strange supermarket where she did not know where the washing powders
were. Enzyme containing washing powders are well known to cause
problems, but she never used them. After admission to hospital for
investigation she recovered completely in a few days, so a
provocation test was carried out getting her to by pour the powder
from one plastic cup to another to create a little dust.
she had an immediate and very severe reaction to the scented powder,
and a reaction lasting five days to the unscented. As she washed
twice a week she constantly had asthma until the powder was proved
to be the cause and she found an alternative. The actual chemical
involved was never identified, but this unusual case suggests that
less extreme cases probably exist which are not diagnosed. It was
obvious that perfumed powder was much worse than unperfumed, as she
had observed herself.
On the way to his office in Nottingham in the morning this patient
sometimes offered a lift to any young ladies waiting for the bus.
He discovered that if they were wearing scent he would have quite
severe asthma by the time he got to his office five miles away.
This deliberate provocation test clearly proved that he would have
to avoid ladies wearing scent. This case was obvious, but how many
milder cases are not recognised? I have never found a woman with
this complaint, except to washing powder!
Environmental pollution can have serious secondary effects on the
ecology of birds, plants, and insects. The most recent example is
that a drug often used for arthritis, Voltarol (Diclofenac), has
decimated the vulture population of India.
This is because traces of
the drug in the flesh of sacred cows treated with Voltarol are
enough to cause kidney failure in vultures, thus causing a public
health problem because the vultures had an important role in keeping
the country clean.