Inflamed, itchy armpit rash?

it started with a dull razor but it wasn't bad, just a little redness it didn't irritate me. then i used my sister's deodorant and it itched sooo bad, i was digging at my armpits all day and they became red, swollen with bumps, and they were sensitive to anything touching them including sleeves. Now it's two days later, i washed my armpits really good and used a new razor to shave and used my own deodorant (which is for sensitive skin since this rash has occured before) but it's still there itching just as bad, burning, red with bumps. should i see a doctor/dermatologist or just give it time?