How Can I Know If I’m Allergic To PEG?

Hi, I m a 25 year old male. I have a moderna covid shot scheduled for April 3rd. I read that people with an allergy to PEG should not take mRNA vaccine shot, but how do I know if I m allergic to PEG in the first place. I did some research and I found PEG is in my moisturizer which I ve been using regularly without any issues and my shaving cream. Does that mean I m not allergic ? I m confused because unlike my moisturizer, the vaccine enters my blood stream