The Effect of Nasal Steroids and Antihistamines on Asthma Control in Patients with Asthma and Comorbid Allergic Rhinitis: A Systematic Review

Abstract

ABSTRACT

Background Asthma and allergic rhinitis (AR) frequently coexist, with studies reporting comorbidity in over 75% of adult asthma patients. In the United Kingdom (UK), more than 80% of adults with asthma also experience AR symptoms. This overlap contributes significantly to the healthcare burden, with asthma alone costing the National Health Service (NHS) an estimated £1.1 billion annually. Across Europe, the annual cost of managing severe asthma with coexisting AR exceeds €9,000 per patient. Although intranasal corticosteroids (INCS) and antihistamines are widely prescribed for AR, the definition of their direct effects on asthma outcomes in adults with both conditions remains insufficient.

Methods This systematic review included randomised controlled trials (RCTs) assessing the effects of antihistamines or INCS on asthma outcomes in adults with comorbid AR. Four databases – PubMed, MEDLINE, Embase and Google Scholar – were searched from inception to May 2025. Outcomes assessed included asthma symptom scores, lung function (FEV ₁ , PEFR), rescue medication use, bronchial hyperresponsiveness and biomarkers. Meta-analysis was conducted when at least two studies reported comparable data; otherwise, a narrative synthesis was employed. Risk of bias was assessed using the Cochrane RoB 2 tool, and evidence certainty was evaluated by using GRADE.

Results Ten RCTs – six on antihistamines and four on INCS – met the inclusion criteria. Meta-analysis of seven studies reporting asthma symptom scores showed a pooled standardised mean difference (SMD) of -0.55 (95% CI: -0.67 to -0.43), favouring intervention. Subgroup analysis showed SMD of -0.51 for antihistamines and -0.87 for INCS. While the antihistamine effect remained robust in sensitivity analysis (SMD = 0.55; p = 0.02), the INCS effect remained statistically significant in its sensitivity analysis (SMD = -1.01; p = 0.001).

However, the subgroup comparison did not reach statistical significance (p = 0.06). GRADE rated the certainty as moderate for both antihistamines and INCS meta-analyses. Other asthma outcomes – including FEV ₁ , PEFR, rescue use, bronchial hyper-responsiveness, and biomarkers – were inconsistently reported and narratively synthesised, with low to very low certainty.

Conclusions Antihistamines and INCS may offer modest improvements in asthma symptom control in adults with coexisting AR, although strong evidence is limited – particularly for INCS. Further high-quality RCTs with standardised asthma outcomes are needed to clarify their role in integrated asthma-rhinitis management.