My son got little red bumps all over him and he is starting to itch what could it be and how do I get rid of it?

Too many to list. The skin is limited in the things it will do. Bump/blister/bruise/pustule etc. All have many possible origins & most are best sorted out with a gathering of historical information ( how it started, exposures, etc.) followed by an exam. Location and character of the bumps are sometimes specific & sometimes not. The itchy ones are more often part of an allergic response have it seen if it persists.