It’s most likely your energy opening up, you are feeling your chi or Parana.
Look it up no mater if you believe in it or not, I’m sure you will be be a believer.
Only thing I think you should know is, relax and let the feeling do what it does, and
Relax your mind and body. And when your done put your right hand on the belly and the left on top of it and breath deeply, focus on your belly, It will draw your chi there and
Store it. It’s not recommended to leave it out in other body parts.
Oh and it’s does heal your body I believe if you keep this up you won’t need any of that
Antihistamine.