Patients with severe asthma produce special substances in their airways when taking medicine during an asthma attack that block the treatment from working. Two different so-called growth factors – naturally occurring substances that stimulate cell proliferation – activate as they inhale corticosteroids used as an emergency treatment during such an attack. The discovery was made as researchers investigated an enduring mystery in asthma treatment: Why do some patients who suffer the most from the disease often have the least success with conventional rescue treatments? To read the full story.