May 4: World Asthma Day

Manuel Van den Broucke, sports, society and politics correspondent, May 4, 2025

What Is Asthma?

Asthma is a chronic inflammatory disease of the airways caused by obstruction of the bronchi. Cells called mast cells release histamine, a substance that causes the inner lining of the bronchi to swell and the surrounding muscles to contract. At the same time, eosinophils (specialized white blood cells) secrete enzymes that thicken the mucous membrane, further narrowing the airways. Forced expiratory volume (FEV1) then drops by 20%, leading to wheezing, a feeling of chest tightness, and, if untreated, a drop in oxygen saturation that can cause fatigue, dizziness, or bluish lips. During a severe attack, the increased effort to breathe can lead to hypercapnia, a buildup of carbon dioxide in the blood, which causes drowsiness and confusion.

Main Causes of Asthma

Genetically, some people inherit genes that promote the production of IgE antibodies, which overreact to common allergens such as dust mites, pollen, or pet hair. Air pollution, particularly fine particles and nitrogen oxides, causes chronic irritation of the bronchi, increasing the likelihood of an attack. Finally, certain viral infections, such as respiratory syncytial virus (RSV), can damage the bronchial lining and encourage asthma symptoms to develop.

Available Treatments for Asthma

Inhalers contain a bronchodilator (such as salbutamol) that quickly relaxes the muscles of the bronchi to open the airways. Maintenance inhalers, taken daily, release a corticosteroid (such as budesonide) that reduces inflammation over the long term. These corticosteroids work by inhibiting the transcription of genes coding for inflammatory mediators, such as cytokines and chemokines, reducing swelling and cell infiltration in the bronchial walls. For severe cases, monthly injections of targeted antibodies (omalizumab or mepolizumab) may be prescribed. Omalizumab works by binding to free IgE in the blood, preventing it from attaching to receptors on mast cells and basophils, which blocks the allergic activation.