Such inhalers could be ready within five years if the research proves effective in humans.
Mice that had been treated to give them asthma-like attacks developed far less severe symptoms after inhaling DNA from bacteria.
Most present treatments for asthma focus on reducing the inflammation of the bronchial tubes, which become affected in an immune response whose cause is still unclear. A potential vaccine is undergoing trials at a London hospital.
Now, a new treatment for sufferers is proposed by a team at the University of Iowa.
Dr Joel Kline, a lung expert at the university, told New Scientist magazine that the body was programmed from birth to recognise the DNA of invasive bacteria and some viruses. He explained: "Your body can't wait weeks for a specific antibody to be produced to begin attacking."
Early exposure to bacteria, and stimulation of an antibody response is thought to stop people developing asthma later in life.
Dr Kline's work aims to prompt the response by using bacterial DNA. An experiment with mice, sensitised to develop asthmatic symptoms when they encountered a protein from eggs, showed that sniffing short sections of DNA from bacteria, mixed with the protein, did not lead to symptoms.
Dr Kline also found that the number of white blood cells entering the lungs and causing inflammation fell to 10 per cent of previous levels.