Not to, um, dim your hopes, but it's doubtful.

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I recently stayed at a hotel where there were lamps made of salt blocks, said to relieve allergies and purify the air. Is this for real?

Not to, um, dim your hopes, but it's doubtful. Believers claim that these glowing lamps—the body is a hunk of orangey rock salt, and there's either a lightbulb or a candle tucked inside—emit negative ions, which bind to positively charged dust and allergens in the air and can alleviate myriad ailments. But there's simply no good science to back any of this up.

That said, salt water does have a long history of healing; for example, rinsing nasal passages with saline can help loosen mucus and reduce dryness and inflammation. But if you spring for a lamp, use it for the mood lighting, not the medicinal benefits.

Health’s medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.