you mean carrier oils from injecting a ton of gear or actual synthol? because synthol stays in the muscle, doesn't dissapitate(it's meant to stay ofc)and causes all kinds of problems in the long run. There are studies about this. Necrosis of healthy tissue and what not.
But I mean if they Inject like 20+CC of gear in the delts that is alot of oil and will have a notable local swelling.
But yes I see some suspect side delts most notable last Olympia Hadis. Some others too but not as obvious.
There is no evidence that the oil (mct) doesn't dissipate. In fact many UG gear labs use MCT for their steroids because it's thin and supposedly easily dissipates. There are some ingredients in some of these oils to make it stay a little long, silica or collagen etc.
What I'm fairly positive about is that these site enhancement oils do is cause the muscle to produce massive amounts of scar tissue. That's the "permanent" part you see, although some of the size goes away once you stop. The sellers used to claim that once you stretched the facia with the oil the "empty" space would then fill up with real muscle, but most will now discount this theory.
Another factor to consider is how much oil you need to inject to create the Synthol effect. There are these plans on how to go about it on professionalmuscle. At some point you may be injecting like 9ml in biceps only per day, if I'm not mistaken (don't quote me on that) but my point is that you don't get these effects by mistake, it's hard work lol and most give up. Some don't get any effects regardless.
One bb by the name of Dusty Hanshaw claims he was able to create a lot of scar tissue in his triceps with Winstrol but that it didn't workfor his delts. Winstrol of course is a water based suspension, I think the crystals can cause some damage and the muscle responds with scar tissue. A heavyweight bb may use 20ml of more of gear per week but that's not enough to grow you arms and delts as much as these guys do, but sure, it may cause some "size" (damage) over the long term and everyone site injects, but for the pros it's mostly muscles like the lats, apart from the common ones.
So IMO almost all use and have used site enhancement oils in their delts in particular, because today you need delts where the rear delts can be seen from the front lol.
I have to comment on what joswift said, I haven't seen evidence nor heard of a possible mechanism whereby the kidneys could be damaged by medium chain triglycerides. If it was true you could damage your kidneys eating coconut oil.
What do you think about the "scar tissue hypothesis"?
Then there are the more temporary enhancements for shows:
https://www.instagram.com/reel/C8X7_3wuf_l/?igsh=MWJpMzdkZnpiYjZ0dg==https://www.instagram.com/reel/C8aXLWhSPVX/?igsh=MWhsMHNldmZha3VtbQ==