Dimetindene is an antihistamine medication used to treat allergy symptoms. However, as with any medication, it is important to ensure that it is free from impurities. Dimetindene impurities refer to any unwanted substances that may be present in the medication, such as by-products or contaminants. These impurities can affect the safety and efficacy of the medication, which is why it is important to monitor and control the levels of impurities in dimetindene.