Investigation of the Effects of a Multispecies Probiotic Formulation on Perennial Allergic Rhinitis

The goal of this clinical trial is to learn if a probiotic formulation consisting of multiple bacterial strains has a positive effect on the quality of life of participants with chronic perennial allergic rhinitis symptoms. The researchers will also study whether the probiotic formulation influences the symptoms of allergic rhinitis. Participants with allergies to house dust mite, cats and/or dogs will be included in the study. The main questions it aims to answer are: Does the probiotic formulation have an impact of the quality of life of the participants? Does the probiotic formaluation have an effect on the severity of the symptoms of allergic rhinitis? Are there differences in the effects depending on the allergies the participants have? Researchers will compare the probiotic formulation to a placebo (a substance that contains no probiotic bacteria but looks, smells, and tastes the same) to see if the probiotic formulation improves the quality of life of participants with chronic allergic rhinitis. In addition, also a GI symptom questionnaire will be filled in by the participants weekly Participants will visit the clinic for the screening, and at the start, and at the end of the intervention for checkups and sampling. During the intervention they will take the probiotic formulation or a placebo twice every day for 12 weeks. They will keep a diary of their symptoms and note whenever they use anti-histamines and every two weeks they will fill in a questionnaire about their quality of life.