For some reason, that research has failed to identify, the immune system mistakes a harmless substance for a pathogen and tries to kill it. These harmless substances are allergens like pollen, cat hair or dust mites. The allergic symptoms like runny noses and watering eyes are the direct result of the immune system trying to defend the body from these harmless substances. The entire allergy industry is geared to treating allergies through the use of drugs. They have many side effects and are only marginally effective.
Many people suffer allergies.
Over 50 million people have them. Many people have been to the allergist, taken the tests, tried the shots, taken prescription drugs and over the counter medications and still suffer from allergies. They are tired of the side effects from the drugs and constantly dealing with the lingering allergies and related sinus problems. The concepts of advanced hygiene take a simple, low tech, common sense approach to this problem. If you are allergic to a substance, why not use better cleansing techniques to keep that substance away from your body and thereby not triggering an immune system response.