Launched in February, the daily-use spray follows the reclassification of Nasonex, from prescription-only medicine to a pharmacy medicine in 2017.
Clarinaze is the only product containing mometasone that is available without a prescription, Bayer claimed.
The spray is designed to prevent and relieve symptoms of allergies, such as sneezing and an itchy nose, the manufacturer said.
It takes between 12 and 48 hours to work and can be used up to two days before the start of the pollen season, Bayer continued.
The launch is being supported by a £1 million marketing campaign that includes training for pharmacy staff, it said.
One 18g Clarinaze pump spray retails at £13.99.
To order, contact your wholesaler.