I am taking cilantro by concentrated drops which are made from organically grown cilantro and sold by a company called Herb Pharm. I bought them on Amazon.com. Since I started my regimen of 5 drops twice per day, my Grover's sores have faded in color and most of them are bothering me far less than before. I am hoping for continued improvement over time. However, I can't be sure that the drops are the reason for my improvement since it is also possible that it is just coincidence. Would you mind telling us which cilantro oil you are taking? Also, I echo what someone else just mentioned about going back and reading posts on this forum from the past starting in late February of 2019. I think this link will take you there: https://connect.mayoclinic.org/discussion/grovers-disease-247ffc/?pg=11#comment-114878
Pay particular attention to @kimass1 and @gardeningjunkie , but there are several other great contributors as well. They have all used fresh cilantro and have made smoothies using it. The details on how to do that are back there if you continue reading the posts going forward. Eventually, the Grover's of @gardeningjunkie went into complete remission, and she has estimated that the cilantro smoothies have helped about 50% of those who have tried them.
This may be a better way to go for you if you are willing to go to a little extra trouble of going through this process.
Obviously, the drops are far easier, but I seem to be the only one trying this experiment, at least at the moment. I seem to recall one other mention of them in these past posts and the person said they didn't work in his/her case, but
they didn't say exactly which drops they were taking, so I concluded nothing from that. I'm glad to have you running this experiment with me and I hope you have continued success, but please let us know exactly what you are taking.
By the way, you are right about your doctor not knowing what to do. They can try to treat the symptoms, but that's it.
It is up to us to try to find solutions. Good luck!