Bma Illustrated Medical Dictionary

childhood and may develop in associa-

tion with eczema or certain other

allergic conditions such as hay fever

(see rhinitis, allergic). Susceptibility to

these conditions frequently runs in fam-

ilies and may be inherited.

Some substances, called allergens, are

known to trigger attacks of allergic asth-

ma. They include pollen, house-dust

mites, mould, and danderand saliva

from furry animals such as cats and

dogs. Rarely, certain foods, such as

milk, eggs, nuts, and wheat, provoke an

allergic asthmatic reaction. Some peo-

ple with asthma are sensitive to aspirin,

and taking it may trigger an attack.

When asthma starts in adulthood,

there are usually no identifiable allergic

triggers. The 1st attack is sometimes

brought on by a respiratory infection.

Factors that can provoke attacks in a

person with asthma include cold air,

exercise, smoke, and occasionally emo-

tional factors such as stress and

anxiety. Although industrial pollution

and exhaust emission from motor vehi-

cles do not normally cause asthma,

they do appear to worsen symptoms in

people who already have the disorder.

Pollution in the atmosphere may also

trigger asthma in susceptible people.

In some cases, a substance that is

inhaled regularly in the work environ-

ment can cause a previously healthy

person to develop asthma. This type is

called occupation asthma and is one of

the few occupational lung diseases that

is still increasing in incidence.

There are currently about 200 sub-

stances used in the workplace that are

known to trigger symptoms of asthma,

including glues, resins, latex, and some

chemicals, especially isocyanate chemi-

cals used in spray painting. However,

occupational asthma can be difficult to

diagnose because a person may be reg-

ularly exposed to a particular trigger

substance for weeks, months, or even

years before the symptoms of asthma

begin to appear.

Asthmatic attacks can vary in severity

from mild breathlessness to respiratory

failure. The main symptoms are wheez-

ing, breathlessness, dry cough, and

tightness in the chest. In a severe attack,

breathing becomes increasingly difficult,

resulting in a low level of oxygen in the

blood. This causes cyanosis(bluish dis-

coloration) of the face, particularly the

lips. Untreated, such attacks may be fatal.

There is no cure for asthma, but at-

tacks can be prevented to a large extent

if a particular allergen can be identified.

Treatment involves inhaled broncho-

dilator drugs (sometimes known as

relievers) to relieve symptoms. When

symptoms occur frequently, or are

severe, inhaled corticosteroidsare also

prescribed. These drugs are used con-

tinuously to prevent attacks by reducing

inflammation in the airways and are

also known as preventers.

Other drug treatments include sodium

cromoglicateand nedocromil sodium,

which are useful in preventing exercise-

induced asthma. A new group of drugs

called leukotriene receptor antagonists

may reduce the dose of corticosteroid

needed to control the condition. Theo-

phyllineor the inhaled anticholinergic

drug ipratropiummay also be used as

ASTHMA

A

NORMAL AIRWAY

AIRWAY DURING ASTHMA ATTACK

Normal air passage

Thin layer

of mucus

Relaxed

muscle

Contracted

muscle

Narrowed

air passage

Excess

mucus

Mucus-producing cell

ASTHMA

ASTHMA