Those random itchy bumps on your arm sound like you have Keratosis pilaris which is a skin condition caused by an overgrowth of Keratin which is a protein.
Keratin causes small red bumps to form around hair follicles on your body including your arms.
You can get rid of Keratosis pilaris by applying some apple cider vinegar or baking soda and salt to the bumps.
Olive oil also works to get rid of Keratosis pilaris.