Synthol, which is a mixture of triglyceride oils and benzyl alcohol, was originally intended as a form of “posing oil” for bodybuilders. When injected into a muscle, however, the body is slow to break it down, so giving an inflated appearance...Link (via We Make Money Not Art)
“Also, because it gives a fast swelling, you will get cramp from a squashing of the nerve. Then you can get crushing of the actual blood vessels and blood flow cut-off.” Some authorities in the US have said bodybuilders also risk giving themselves a pulmonary embolism, which can be fatal, by injecting synthol directly into a major blood vessel.
Update: Mark sez, "The bodybuilder in you picture is Gregg Valentino. He denies taking Synthol in much the same way Lance Armstrong points out he has never tested positive. Steroid abuse by American kids is on the increase, just as they are doing less sport. Are they emulating celebrities? Stallone was recently busted for having illegal Human Growth Hormone, while Anna-Nicole Smith also took HGH. Gene doping, meanwhile, is already with us."