Yes. All drugs have potentially dangerous effects—it depends on how much you take and how you take them. Generally, the amount of over-the-counter drugs you need to take for the intended action (like getting rid of an allergy) is much less than would produce a harmful effect. That is why the U. S. Food and Drug Administration allows these drugs to be sold without a prescription. But if you take a larger amount, the drug could very well cause harmful effects and even death, particularly if combined with other drugs or alcohol.