As I just said, Himalayan salt lamps are inherently fragile. Once you own one, you definitely need to be careful not to drop it or bang it into other solid objects because the salt crystal can be damaged very easily. This is actually a rare time when durability is not desirable. If your salt lamp is unaffected by a collision, it could likely be an imposter.
It is possible that the negative ions released by Himalayan salt lamps may protect against airborne germs. In addition to removing these contaminants from the air, the salt also allows the body to filter air more effectively in an attempt to block any foreign particles from making it into the lungs. This can prevent the advancement of coughing, sneezing, sore throats, and other minor symptoms of the common cold. 
This brings me to my next point. Atoms and molecules are less reactive when their valence electrons are organized in pairs. If they have an odd number of valence electrons, or if they have a few that are not paired together then they are called “free radicals” (Wikipedia). This does not mean that free radicals are only cations (positive ions). They can be cations, anions, or neutral. For example, neutral sodium atoms have one unpaired electron which can participate in chemical reactions with other elements, and Methylene (CH2), has two unpaired electrons on the central carbon atom. Free radicals are also not all bad. Wikipedia also states that free radicals play a key role in biology where they help to regulate the body. Usually when people talk about harmful free radicals they are referring to oxidants which loosely speaking are molecules which take away electrons from cell membranes, proteins, and DNA (cancer-causing mutations) in the human body. This is probably where the idea of free radicals being positive ions comes from because they like to steal electrons.
A few isolated studies have shown modest and equivocal effects from negative ionization. For instance, in 1981, researchers at the University of Surrey in England looked at the incidence of stuffiness, nausea, dizziness and headaches in people in an office environment. They found office air had fewer negative ions than is typical outside. So the team conducted a double-blind study and found that the reintroduction of ions reduced the incidence of these symptoms over a 12-week period. The findings were published in the Journal of Environmental Psychology. A 1993 study published in the Journal of Human Ergonomics found that negative ions could slightly affect people's circadian rhythms, although they had no impact on anxiety or exercise levels.
Everyday appliances such as televisions, cell phones, computers and tablets release positive ions into the air constantly. These and other common electronics can cause an overflow of electromagnetic radiation (EM), which, although invisible, is believed to cause some serious long-term effects. Constant exposure to EM radiation is known primarily to cause fatigue, increase stress and weaken the immune system. Himalayan salt lamps emit negative ions and cancel out positive ones. Therefore, by neutralizing electromagnetic radiation, they help reduce artificial frequencies and even prevent static buildup. 

Please note: Each Natural Himalayan Salt Lamp is unique and as such, each lamp's color, size and shape will vary. Natural Himalayan Salt Lamps weigh anywhere from 7 to 11 lbs. These salt lamps can “sweat” in very high humidity environments, and are made with North American plugs which use 110v power. If you live in Europe or elsewhere outside the U.S., you will need to obtain an adapter.
As for the idea that water vapor in the room attracts pollutants, then sticks to the surface of the lamp, that, too, makes little sense, he said. Some pollutants in the air might, by chance, stick to water vapor on the surface of the lukewarm piece of rock salt, but there's no evidence that the meager heat produced by a light bulb could produce significant amounts of pollutant filtering, he said.
Remember, even if you’re like me and you can’t sleep unless the room is totally dark, you can always turn the lamp off at bedtime. Just leave it on for the rest of the day so it can do its work while you’re awake. People in humid climates should be aware that HPS lamps tend to weep when the salt becomes cool. You’ll definitely want to protect surfaces by placing a saucer underneath and be sure to follow the instructions for use and care which should be included with your lamp!

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After having this salt lamp for two months, the light bulb make a loud noise and sparked. I tried putting in a new bulb and it still wouldn't work. This ended up happening to three of the five salt lamps we purchased (I purchased five of these at once from this seller). I tried getting in contact with the seller and they never responded so now I'm stuck with 3 salt lamps that can't be used.