One of the most common causes of a clogged bathroom drain is hair, and the thought of pulling out clumps of tangled locks makes most people run for the Drain-O. But common drain cleaners pack a toxic punch. They contain sodium hydroxide and sodium hypochlorite, which can cause permanent damage to skin and eyes on contact, and the vapors can burn lungs. Many also contain dimethyl benzyl ammonium chloride, a severe eye and skin irritant, and dichlorodifluoromethane (uh, what?), a neurotoxic eye irritant.
So instead of pouring poison down your drain (which can also leak into the environment), you should create your own, non-toxic drain cleaner with baking soda and vinegar. First, remove any visible debris. Then pour about a 3/4 cup of dry baking soda down the drain, followed by a 1/2 cup of vinegar. Immediately plug the drain with a stopper or rag, and let it sit. The reaction from the baking soda and vinegar will break down gunk. After about 30 minutes, pour boiling water down the drain.