I can only speak from personal experience but growing up partially in a hospital, my doctors took an approach that today might seem irrational and might even result in malpractice. They told my parents to let me play in dirt, drink muddy water even, take part in activities that might cause an asthma attack, don’t fret over Cloroxing every surface. I haven’t had a severe asthma attack in 12ish years and no longer take steroids for allergy control. I’ve never met a person with asthma as severe as mine but I’ve met plenty who still have to keep an inhaler on hand.