Carrageenan-containing nasal spray alleviates allergic symptoms in subjects with grass pollen allergy: A randomized, controlled, crossover clinical trial

Purpose Nonpharmacological nasal sprays forming a barrier between allergens and the nasal mucosa are used to manage symptoms of allergic rhinitis. We aimed to evaluate the safety and effectiveness of Callergin, a nasal spray containing barrier-forming iota-carrageenan, in the treatment of allergic rhinitis. Methods In this randomized, controlled, crossover trial, we assigned adults with grass pollen allergy to receive Callergin, VisAlpin and no treatment in a random order for three consecutive periods, separated by a washout period of 7 days. Subjects prophylactically applied one puff of nasal spray to each nostril 5-10 minutes prior to challenge. The primary endpoint was mean change from baseline in ‘total nasal symptom score’ (TNSS) over 3 hours, a sum of rhinorrhea, itching, sneezing, and congestion scores, recorded every 15 minutes during the challenge period. Results A total of 42 subjects underwent randomization. Exposure to grass pollen for 3 hours led to a notable TNSS increase from baseline in all subjects at all times. Mean TNSS was lower when subjects received treatment with Callergin compared to no treatment, although the difference did not reach statistical significance (untreated 6.96 ± 2.30; Callergin 6.59 ± 1.93; difference 0.37 points [95% CI -0.17 to 0.91]; p=0.170). In a post-hoc analysis, mean TNSS at 3 hours was significantly reduced with Callergin treatment compared to no treatment (untreated 8.29 ± 2.64; Callergin 7.70 ± 2.56; difference 0.60 points [95% CI -0.10 to 1.29] p=0.028). While all individual nasal symptoms contributed to this effect, rhinorrhea (p=0.013) and congestion (p=0.076) contributed the most. Consistently, nasal secretion weight was slightly reduced with Callergin (p=0.119). VisAlpin improved nasal symptoms, but not significantly in either analysis. The incidence of adverse events was similar among treatment groups. Conclusion Prophylactic treatment with Callergin is safe and alleviates nasal symptoms in adults with grass pollen allergy. Trial registration NCT04531358