I've had about 100 progesterone in oil injections and never had any issue. Despite dire warnings about the sesame oil that it is in, I never reacted in any way, other than some discomfort at the injection site as the PIO got absorbed into the surrounding muscle.
The 17P injections aren't quite the same as the PIO I used, but the 17P is also progesterone in oil. And now? I am itching like MAD at every injection site. It's worst very shortly after the injection is given, and it starts to fade toward the end of the week, and then when I get the next injection, it's all itchy at that site, as well as all the other injection sites that have been used. It is maddening.
Fortunately, this is but a minor issue for the moment, but it's still annoying.