Asthma
Around half of the 300 million global estimates of asthmatic population live in Asia. Asthma is a lung airways disease with periodic symptoms and often with nocturnal attacks. Symptoms may be produced by exposure to allergens and physical exertion. Asthma is defined as follows: (1) Airways obstruction that is reversible (but not completely in some individuals) either spontaneously or by treatment; (2) the presence of inflammation in the airways mucosa by inflammation-causing cells such as eosinophils, mast cell, macrophages, and T-lymphocytes; and (3) increased airway responsiveness to a variety of stimuli. The increased abnormal hyperactivity of the airway may be caused by many stimuli including: aero-irritants (cigarette smoke, diesel fumes, nitrous oxide and others), weather changes, stress, drugs (aspirin, antibiotics and others), emotions and viral infections. These stimuli cause increased production of mucus and contraction of the bronchial muscles resulting in difficulty in breathing out because of obstructed airways passage. Asthmatic individuals develop clinical symptoms such as chronic cough, wheezing and hoarse voice, after exposure to allergens, environmental irritants, viral infections, cold air or exercise. One study indicated that 80 percent of asthmatics had concomitant rhinitis. Asthma risk doubled when rhinitis developed in the first year of life compared to when rhinitis was diagnosed later in life. Patients not treated for allergies have a 61 percent increased risk of being hospitalized compared to those who received treatment.

Asthma may be broadly grouped into allergic asthma and non-allergic asthma. Some asthmatics may have both types. In Malaysia about 80 to 90% are allergic asthma mostly noted in children and young adults, and 20% are non-allergic asthma that is frequently found in middle-aged and elderly individuals. The non-allergic asthma develops spontaneously during adult life. Several features can distinguish the two types of asthma. In allergic asthma, there is a family history of allergy or asthma, the total and specific IgE antibody levels are raised, the onset of symptoms is immediate, and the clinical course is mild. In contrast, in non-allergic asthma, there is no family history, IgE antibody levels are within normal range, the onset of symptoms is delayed, and the clinical course is severe. Moreover, non-allergic asthma occurs more commonly in females, and is frequently associated with aspirin sensitivity and presence of nasal polyps. Both types of asthma manifest raised levels of eosinophils in the bronchial mucosa.

In allergic asthma, inhalation of allergens such as house dust mites, cockroach or cat dander, is the most important stimulus known to trigger the disease. In sensitized individuals the allergens trigger an immediate asthmatic response during which bronchi-constriction develops within 10 minutes, reaches maximal contractions in 30 minutes and then usually resolves in 1 to 3 hours. In about 50% of adults and 80% of children with the response, a late asthmatic response (bronchi-constriction) follows.  The asthmatic attack recurs at 3 hours and lasts for 24 hours if untreated. Patients with late phase asthma triggered by allergens, go on to develop hyper-responsiveness that last for days or weeks. Patients, who only develop the early phase asthma but not late phase response, do not have bronchial hyper-responsiveness.

From the Malaysian context, analysis of the response to specific allergens in children with asthma showed that 90% reacted to house-dust mites allergens, 67% reacted to cockroach allergens, 23% to cat dander or dog epithelium allergens, and 10 to 22% to cows milk, soya bean, egg, peanut, fish, shrimp, crab, banana, and wheat. Thus, it is important to obtain a complete allergen profile for the asthma patient so that appropriate avoidance measures can be taken as part of the management programme for the disease. Here are some important points worth considering: