Causes of asthma Part 1-By Dr.Karim
It is chronic inflammation of the respiratory airways characterized by:
– Air flow obstruction that is reversible either spontaneously or with treatment.
– Airway hyperresponsivensess to many stimuli.
– Genetic predisposition (it tends to run in families).
It is the most common chronic respiratory disorder among all age groups.
Chronic is a medical term which means that this disease tends to persist more than 3 months. Another example of chronic illnesses are hypertension (persistent high blood pressure above 120/80 ) and diabetes mellitus (persistent high plasma glucose level above 110 mg/dl after fasting for 8 hours).
Inflammation means redness, hotness, swelling, pain and loss of function of the affected organ. It is an immune system response to any harmful stimuli such as injury, infection and irritation. Inflammation is a beneficial response as the inflamed organ gets increased blood supply through the dilatation of its supplying blood vessels. This helps in increasing the rate of organ repair.
Blood carries red blood cells, white blood cells, neutrophils, basophils …..etc. The first blood component to reach the inflamed site is the neutrophils which secrete certain chemicals – called cytokines- that kill the causative organism. These cytokines might also cause some damage to the organ itself.
Remember :Redness and hotness are due to increased blood supply , pain and swelling are due to cytokines.
The cause of chronic inflammation in asthmatics is that they have hypersensitive (hyperresponsive) airways. This means that their airways respond to normally harmless stimuli with an inflammatory response, thus their airways are persistently inflamed.
The causatives of asthma can be divided into 2 categories :
A. Extrensic (Allergic) :
These always appear during early childhood.
Dust: Although dust itself isn’t an allergen , there are allergic components in it as dust mites. These are small insects found in dust in the wardrobes, carpets, curtains, soft toys. Asthmatics should properly ventilate their homes. They are the most common type of allergens.
Pollen: which comes from plants in their mating season in Spring. Asthmatics should wear protective masks during spring.
Pets: such as cats and dogs. Dander from these animals cause bronchial asthma. This type of allergen is prevalent in many countries as many keep pets in their homes. Good news for cat lovers is that a number of epidemiological studies suggest that close contact with a cat or dog in very early infancy reduces subsequent prevalence of asthma later in life.
Cockroaches: prevalent in tropical environments.
Tobacco smoking: and passive smoking. It is an important risk factor in the development of childhood asthma. The earlier and the greater the degree of exposure to tobacco smoke, the greater the likelihood of developing childhood asthma. Smoking during pregnancy also causes an increased risk of the infant to develop bronchial asthma later in life. This is due to the growth retardation of the lungs caused by persistent exposure of the infant’s lungs to nicotine.
Air pollution: Asthmatics shouldn’t live close to factories and streets crowded with vehicles.
Remember: These allergens are normally harmless stimuli to normal individuals. They only cause bronchial asthma in patients with hyperresponsive airways(asthmatics).
This tends to occur later in life . It is usually secondary to recurrent chest infections and it tends to be triggered by exposure to cold air, dry air, laughing, coughing and psychological factors as anxiety, fear.
In infants, the principle cause of bronchial asthma is viral respiratory infections rather than allergens.
Respiratory syncytial virus (RSV), Parainfluenza and Rhino virus ,during the 1st 2 yrs of life.
Influenza virus which is much more common in older children and adults.
Non-steroidal anti inflammatory drugs (NSAIDs) as aspirin, ibuprofen, piroxcam, diclofenac sodium.