Doctors inject stuff like antibiotics, vaccines, and painkillers into the delts. There is a big difference between that and some idiot bodybuilder injecting huge amounts of oil into his delts for years on end. It might be safe, but it will seriously deform the muscle after a while.
Who are you calling an idiot?
You don't know what you're talking about, bro. If you rotate injection spots regularly and take care to avoid abcesses, you'll notice no muscle deformation at all. If you inject into one particular muscle on a regular basis for years, you will eventually stretch the fascia, which only gives the muscle slightly more room to grow. (This is especially true of irritant-steroids that promote inflammation.) Even in the most extreme cases, you'll not be left with an odd-looking muscle -- just a marginally larger one.
(Unless you forgot to rotate injection spots and have accumulated scar tissue... In which case, you should have been more careful.)
