Marketed as a "posing oil," a single bottle of synthol and products like it can run between $200 and $400.
"You can buy it online and get it shipped right to your house," Harris said. "Either the FDA has too much going on to pay attention to it, or they really don't know how it's being used.
"If it was actually marketed for its true use, then you would see much more backlash against it."
Telephone messages left with distributors of two such products -- Syntherol and PumpNPose -- were not returned.
Even though it is not currently regulated, some worry that bodybuilders could be putting their health at risk.
"A couple of years ago, there was a case of someone injecting synthol accidentally into a small artery, and he actually killed off part of his muscle," DiPasquale said. "And with any injection, if it is close enough to the nerve, it will disrupt that as well."
Harris agrees, noting that he has read a few reports of people who have used site enhancement oils who have nearly died from complications associated with the injections. And Nadler said that there is a possibility that a user could inject it into a blood vessel, causing a potentially life-threatening embolism.
"I'm sure there has to have been some human deaths because of this," he said.
DiPasquale said that unsterilized needles can also lead to abscesses and infections, as well as the formation of scar tissue.
But he adds that despite the risks, many will still use the product if it means an extra couple of inches on their arms.
"I really don't advise people to use synthol," he said. "It is not something that is recommended, but if someone is going to do it, they're going to do it."
Not all bodybuilders approve of synthol use; in fact, even in this sport where many look to enhancement through pharmaceutical means, synthol abusers are viewed as cheaters.
"Even the ones who use steroids and those who don't are vehemently against synthol use," Harris said. He adds that while steroid users still must eat right and train in order to reap gains, those who use synthol are perceived as taking the ultimate shortcut toward a more massive appearance.
"Even among a group where pretty much anything goes in terms of pharmaceutical use and abuse, even to them this is a scourge," he said. "It's cheating; there's no effort involved."
But Nadler said that though he does not feel the trend represents the bodybuilding community as a whole, he fears those that abuse site enhancing oils are setting a bad example for adolescents and teens interested in bodybuilding.
"I don't think the bodybuilding community has come out strongly enough condemning this sort of freakish appearance," he said.
"It's part of the almost kind of shortcut thinking that goes on with a lot of what's happening in bodybuilding, whether it's abusing steroids or some other substance."
Still, Harris said, the stigma of synthol abuse could be enough to keep many bodybuilders away from the bottle and the needle.
"They really have no allies. They're mocked online on our message boards by other bodybuilders," he said.
"I honestly don't know if some of those guys are not all there, but they're not fooling anybody."