Red Bumps after shaving legs?

I’m not sure if they’re called razor bumps, but I recently starting shaving my legs and they come out fine — but the process where the hair starts growing is when I start getting itchy, and I’m assuming it’s because the hair has friction with the material I’m wearing (pants, underwear, etc) and it ends up leaving red marks, primarily on my thighs. 

Is there a way to prevent this or is it inevitable? Because it makes my legs look so ugly.