Many of us go to pharmacies for headache tablets, cough syrups or allergy treatments. However, over-the-counter (OTC) drugs may cause more harm than good. A newly published journal says many of these medicines may have serious side effects. These include cognitive damage, dementia and even brain shrinkage. This happens in older adults who take OTC medicines for asthma, aches and pains, insomnia and allergies, etc.