Can someone explain to me how come people get asthma?

Dificult question: Many asthmatics developed their condition because of allergies at an early age. The mos common being animal dander, dust mites, seasonal pollen, etc. Family links have been found but exactly which genes are involved eludes us today. There also appears to be an ethnic link involved. As you can see there are many issues involved is asthma. It is more importnat to get treated rather than know the whys.