I don't know why this happens, but I do know it is very common for people to get these sensations during panic attacks. It happened to me. Just know that your body is responding to the fear it is feeling, adrenaline is pumping and you will feel physical symptoms due to anxiety. Try to breath through it, and know that you will be fine!
I know how scarey this all can be. I have suffered from panic attacks for over 20 years on and off.
(I could write a book!) But it would probably be better if you read Claire Weekes books. She really explains the ins-and outs of anxiety and ways to overcome it.
Hope you're better soon.