Another important aspect is the evolution of the immune system. The “hygiene hypothesis” suggests that our immunity developed in conditions of constant exposure to dirt, bacteria, and parasites (helminths). In today’s sterile world, where antiseptics and antibiotics are used, a child’s immune system often becomes “idle.” Unable to find real external enemies, it begins to attack harmless particles (pollen, hair) or the body’s own cells. This explains the explosive rise in allergic and autoimmune diseases, such as asthma, Crohn’s disease, and multiple sclerosis, in urban areas.