Preliminary data published in the Journal of Allergy and Clinical Immunology (https://www.jacionline.org/article/S0091-6749(20)30551-0/abstract) may provide a reason why patients with respiratory allergy and asthma may not experience the severe complications COVID 19 to a large degree compared to patients with other known risk factors such as smoking, diabetes and high blood pressure. This research was brought on by reports from China that suggested that asthma and respiratory allergy were not significant risk factors for their patient population.
Researchers focused on a protein called ACE2 which is found on the surface of cells. The protein may serve as an entry point for coronavirus. They found a decreased presence of ACE2 in the airway of patients with allergic asthma.
As these data are preliminary, further studies need to be conducted to draw clear conclusions. In addition, there are likely additional factors playing a role other than ACE2.