What Causes Itchiness On Leg After Shaving?

Hi doctor, I am 21 this year. I used to have a smooth leg, but all this started to change about a year ago. I've been shaving my leg for quite sometime and recently whenever I shave my legs, it gets really itchy and I'll scratch non stop. Am I allergic to shaving? Now both my leg is awfully cover with scars due to over scratching and bleeding. I need help