If it's an insect bite, you need something topical. If it's an old bite, cortisone creams are probably best. If it's new you can try anti-histamine creams. If you think it's infected go to your doctor ASAP, because then you'll need antibiotic ointments or if it's really bad something internal. I'm not sure how an insect bite gets infected, because it's not really a cut that bacteria gets into, it's an immune system reaction to the insect saliva left behind after you've been bitten, unless you were bitten by something poisonous.