I shaved with shaving cream and I have some redness under my right armpit. I applied intense cream but it's not helping.

It sounds like you may be having an allergic reaction to the shaving cream. One suggestion would be to apply a cream containing hydrocortisone a few times a day for a few days. If you don't see any improvement or if the situation worsens, it's a good idea to see a doctor. Hope this advice helps.