What can cause bad asthma that is not responding to medication?

Difficult to answer: Some asthmatics do not respond well to conventional asthma drugs. This is not totally uncommon. If you are one of them, you may want to see a specialist (pulmonologist) to see if you may need a more unconventional treatment. Good Luck

Refractory asthma: Agree, not all asthmatics are the same. There are things we look for as persistent triggers such as environmental allergens reflux and others that may need treatment as well.

Depends: By far, the most common cause is not taking medications as prescribed. However there are many other factors which need be considered and Xolair has been used with some success for some. Also to be considered is Allergic Bronchopulmonary Mycosis for which a trial with anti-fungal Rx may be tried. Vocal cord dysfunction and aspirin exacerbated resp disease also need be ruled out. Allergy consult?