Exposure to organic
dusts, chemicals, or animals at work can cause the development of
all sorts of allergic responses. The clinical history usually
provides the first clue by the association of symptoms with work,
and recovery with absence from work, but it is seldom so clear-cut
because prolonged reactions are common, and daily exposure adds up
towards the end of the week.
It is very important to make the
diagnosis of occupational allergies as early as possible because if
there is a long delay before diagnosis the asthma may not improve on
removal from exposure, and persist indefinitely.
Allergy to dust
mite or animals as well as to the occupational possibility can
co-exist and confuse the situation, so expert advice on sorting this
out may be necessary.
The best way to illustrate occupational asthma is to publish these
remarkable peak flow charts (below) from a patient with occupational asthma,
which provides clear evidence that the patient is worse at work and
better at home. This is the the most clear-cut example and
instructive example of occupational asthma I have ever
The patient was perfectly controlled to begin with by
using Becotide in a dosage of 200 mcgms twice a day, but all tests
were negative and the cause was not found.. The Becotide controlled
the asthma completely, but this successful treatment actually
obscured the cause of his asthma completely.
I like to control asthma with as little medication as possible,
so I cut the dose at his second visit and suggested that he should
reduce it further if possible. At his next visit his peak flow chart
showed this obvious weekend pattern with worsening from Monday to
Friday, indicating a work problem which was quite unsuspected. This
cause was found to be an isocyanate well known to cause asthma, so he
changed to an
outside job, stopped the Becotide altogether without relapse, and
has had no further asthma. The peak flow charts before and after the
one below are not shown.
The important message from this case is that had the dose not been
reduced he would have continued taking a dose of Becotide which
would suppress the asthma completely, so everybody would have been
happy, for a time. Eventually the asthma would have become more
difficult to control, so more and more drugs would have been
required. Permanent remodelling of the bronchi would eventually occur, so that
even if he changed his job or stopped working altogether he would be unlikely
to recover completely. The cause might never be suspected, and he
would become a chronic “intrinsic” asthmatic, who would never be
diagnosed as industrial asthma.
Allergy to Insects
Insects are very liable to cause allergies, particularly many
species of mites, cockroach in warm climates, ants, and so on.
Locusts are sometimes used for research and the scientists working
with them can become so allergic to them that they have to find
another field of research, as this patient had to do...
Pricking through saliva, blood, and faeces of the insect he brought
to the consultation produced the striking skin reactions shown below
so he had to find another job,
Laboratory workers who work with animals are liable to become
allergic to rats, mice, guineapigs, etc. They are at particular risk
because the main allergen in rats, and probably other animals, is in
the male urine, which dries up and becomes airborne.
This can be a serious problem which can
wreck a promising career linked to the causative animal. In the past
desensitisation could be tried here, but nowadays this method of
potentially curative treatment is not used in the UK., If there is
difficulty in controlling the asthma the victim might have to
consider emigration to get desensitised without changing their
Hairdressers handle many potentially nasty chemicals in the course
of their work, particularly when doing permanent waving, in which persulphates are used.
Hairdressing is not an occupation for the
Skin sensitisation is common, and the future in
this occupation may be compromised.
At right are pictures of the hands
of one such patient.
Healthcare Personnel are increasingly at risk of sensitisation to
latex, as a consequence of greatly increased use of rubber gloves in
recent years. This also applies particularly to children who have
been subjected to many operations, such as for spina bifida.
development of rubber-free vinyl gloves has helped a great deal, but
latex allergy can be very intense, causing all sorts of allergies
including anaphylaxis, and can sometimes be triggered by many fruits
with similar allergen molecules. Further details are easily found on
On the right is an example of a provocation test with two powders
used in making dentures. It is very obvious that pouring the
alginate from cup to cup produced definite asthma, peak flow
dropping from nearly 400 to only 150 after 30 minutes.
development of flexible endoscopes has also entailed the
introduction of sterilisation using Glutaraldehyde, which does not
damage these very expensive instruments. Unless great care is taken
this sterilising agent can sensitise susceptible people, just as
latex has done.
Allergy to Nickel is very common, and can be diagnosed easily
because contact with the buttons on jeans or clips on bras which are
nickel plated produce a rash where they touch the skin.
This case is exceptional, as he was an accountant who got fed up
with his job and bought an old pub. Within few weeks his hands were
as shown in the photograph, with the skin peeling off. The handles
of the old-fashioned beer pumps on the bar were nickel plated, hence
his hands had much contact with nickel.
short course of oral steroids soon suppressed this reaction, and as
he does not touch coins he has had no trouble since the handles were
changed to chrome plate.
The partner of another patient developed eczema limited to the index
and middle finger of the right hand. Her GP wanted to send her to a
dermatologist, but she refused and insisted on seeing me. They had
recently bought a pub, and she was constantly scooping coins out of
the till with these fingers when giving change.
Allergy to wood dusts
Certain woods will cause allergic asthma. The most researched is
western red cedar which has caused much asthma in the lumber mills
in Canada and has been intensively researched. Resin in pine wood
may cause asthma in those who are allergic to pine resin, (colophony).
tropical woods can cause problems if the dust is inhaled, and it is
always sensible to wear a mask if there is a lot of wood dust.
Willow dust has been reported to cause asthma in aspirin sensitive
workers because the wood contains salycylates!
Workshops today are very conscious of the risks of wood dust and it
is mandatory to have effective dust control systems. Before these
precautions were put in place woodworkers were liable to cancer of
the nose, the first part of the respiratory system that dust
In woodworking factories plywood, and various materials
composed of sawdust and formaldehyde resin glues are also a risk
factor for asthma. Colophony, or pine resin, has caused much
occupational asthma when used in cored solder in electronics
factories, and exceptionally in violinists who use it on their bows
to make them slightly sticky.
I had one patient who worked as a secretary to her husband, who ran
a big woodworking shop. She developed severe asthma, all tests were
negative, and it was only by using a peak flow meter and a careful
diary that it became evident that the cause of the problem was in
the office. Although she never went into the workshop enough dust
could get into the office to trigger her asthma. The answer was not
obvious because there was a prolonged delayed effect from exposure
to the office. The actual wood which was the cause of her asthma was