content: You're right, but gallium (Ga) is not as bad as mercury... and mercury (Hg) actually isn't as bad as most people make it, since most people are overly cautious with Hg due to the potential dangers.  For instance, did you know that you can swallow Hg and be fine?  Back in the 17-1800's, people use to swallow it to "clean" out their digestive tracts all of the time, and they'd be fine... the problem is that a couple of people would die because they would have tears in their digestive tracts (or ulcers in their stomach) and the Hg would seep into their blood stream, where it would cause heavy metal poisoning (HMP) and subsequent death. Now, I know that all of that sounds counter-intuitive, but let's explore HMP: Your body requires certain essential minerals to work.  Your heart requires calcium and potassium to beat.  Your brain requires zinc for neurons to work correctly.  Your muscles require potassium to contract and expand.  Just about every organ requires specific minerals to work correctly, and without those minerals, the organs just won't work, and you experience organ failure and death. So, in a very ELI5 way, you can think of these "small" minerals as having a very unique "shape."  This means that a calcium mineral will "fit" ONLY in the calcium "plugs" for each organ, and won't fit into a "plug" for a non-calcium mineral, stopping an organ from getting the minerals it needs. Another important thing you need to know is that these minerals will "evaporate" away as your organs use them.  This means, when that calcium molecule is used up, it goes away to make room for fresh, new calcium, so that your heart can continue to beat. Now... most of your heavy metals can "mimic" the shape of these essential minerals.  This means that an Hg molecule can plug into the receptors of your brain so that your brain can't get the minerals it needs to work correctly.  Hg also doesn't "evaporate" away, so once it's there, it's pretty much there for the long haul.  This all means that, if you get enough Hg into your system, and it finds its way into these "plugs," it can actually starve your organs of the vital minerals they require to function... and your body literally dies from the inside out.  This causes organ failure, and subsequently death. Now, while exposure to Ga can cause dermatitis (inflammation of the skin -- essentially a rash), there have been no documented accounts of Ga causing HMP.  There have even been documented testing sessions where Ga has been injected directly into the blood, without severe issues.  Of course, large "doses" of Ga can be harmful, but drinking too much milk can be harmful (and make you sick), too... anything in excess can be harmful and possibly kill you.