“Chemical drain cleaners are dangerous in so many ways,” says Melisa W. Lai, M.D., a toxicologist at the American Association of Poison Control Centers. “If you swallow some, not only can it burn the esophagus, but it can keep churning through to the windpipe, even the heart.”

This effect, called liquefactive necrosis, might be familiar to anyone who has spilled bleach on his fingers and felt the tips become slippery. “That’s actually the skin cells melting and dying,” Lai says. “And household bleach is a lot less caustic and concentrated than most chemical drain clean­ers.”

Accidents can happen more easily than you think: Use a plunger after chemical drain cleaners and you can splash the chemicals sitting in the clogged sink or drain into your eyes or onto your skin.

If this happens, flush eyes and skin with cool water for at least 10 minutes. Meanwhile, call the nationwide ­poison-control hotline, 800-222-1222. An operator will tell you what else to do and will direct you to the nearest emergency facility. If you’ve swallowed cleaner, Lai does not necessarily advise giving food or liquids like water or milk, despite advice to the contrary on some product labels--such items can be coughed back up, leading to additional burning and choking.

If you resort to chemical products, read and follow the manufacturer’s use instructions and these safety tips:

• Gather all materials, including drain cleaner, tools, measuring devices, and protective gear, before you start.
  
  
• Wear rubber gloves, protective clothing, and splashproof eyewear. Remove contact lenses, which can trap splashed chemicals in the eyes.
  
  
• Open all the windows in the room to increase ventilation and disperse noxious fumes. Leave the room while the chemicals do their work.
  
  
• Never mix one drain cleaner with another or with cleaning products.
  
  
• Recap and dispose of unused portions in the original container with the child-safe cap secured. Do not store leftovers and do not reuse empty containers.