Exposure to substances such as pollen, animal fur or house dust mite can cause your body to produce allergic symptoms. Cells in the lining of your nose release a chemical called histamine when they come into contact with these substances. This leads to inflammation (rhinitis), which produces symptoms such as sneezing and a runny or blocked nose. Ketotifen, an antihistamine, stops the effects of histamine and this helps to relieve these symptoms.
This is a companion discussion topic for the original article at https://patient.info/medicine/ketotifen-zaditen