A salt lamp is simply a chunk of mined salt that has been hollowed out to allow room for a lightbulb or tiny candle. The light glows through the medium of the salt crystal, which can range in color from a dark salmon pink to a pale orange. Salt crystals for salt lamps are mined in Russia and central Europe as well as in the Himalayas. Salt lamps make attractive accent lights. Their main attraction, however, is that the heating of the salt causes the crystal to release negative ions (often called simply 'ions').

Negative ions have long been considered healthy; the sea air, mountain air and the air around swiftly running water is high in negative ions. Indoor air, recirculated air, and air around electronic equipment is very low in negative ions. Many office workers who suffer health complaints around fluorescent lighting and computer monitors report considerably less fatigue and headaches if the concentration of negative ions in the air is increased. Why negative ions may be beneficial is only partially understood.

It has been shown that negative ions in the air bind with airborne pollutants, making them heavier so that they fall to the ground, and therefore are unavailable to be inhaled. Many modern air purifiers - the so-called 'ionic air cleaners' - use this technique to provide cleaner indoor air for allergy sufferers. Some studies seem to indicate that an increase in negative ions in the air increases bloodflow to the brain, which would have the effect of improved concentration. The salt lamp is an attractive alternative to the utilitarian look of an air purifier.

The amount of negative ions a salt lamp can release depends on its size and how warm the candle or lightbulb can make it. The larger the crystal, obviously, the more expensive the lamp, but the larger area it can provide with negative ions. Salt lamps that produce 'night-light' amounts of light can provide ions to an area equal to the average office cubicle.