I have a bite on my leg..that itched a little this morning.and now its bigger and has a bruise around it...what could cause that?

Insect bite: It sounds as though you have been bitten by an insect or a spider. You should keep this area clean and dry, if you notice new swelling, fever, chills, or drainage from the site you should go to the emergency room or schedule an appointment with your doctor as soon as possible. If it gets better on its own then you do not need to worry.