His main scientific activities are research in asthma, allergy and COPD, and he has published approximately 600 original papers on these topics. A central theme in his research is finding means to improve the prognosis for patients with asthma and COPD. The research includes studies on the effects and side effects of pharmacological treatment, such as the issue with inhaled corticosteroids (ICS) and pneumonia and ICS and osteoporosis in COPD and overuse of short-acting beta-2-agonist in asthma. Evaluation of inflammatory markers in asthma and COPD is also a central research theme. One important finding is the value of combining exhaled nitric oxide measurement with blood measurements of eosinophils or eosinophil related proteins in asthma.
His research also includes publications on the performance of inhalation devices, inhalation errors and inhalation technique training. One aspect of this has been to study how to reduce the carbon footprints of inhalation treatment.
Christer Janson is the Swedish Association for Allergology president and an EAACI research and outreach committee member. He is a past chair of the Epidemiology and Environment Assembly of the ERS and scientific advisor for the Swedish National Board of Health and Welfare