Oranges are amazing fruits, and the are primarily rich in vitamin C which has several benefits:
Vitamin C prevents hypertension, and helps to ensure that your blood vessels dilate in a healthy way - thus it is preventative of cardiovascular disease and promotes a healthy heart.
Vitamin C is an antioxidant that helps prevent the eyes from getting damaged. UV rays from the sun cause free radicals to occur within our eyes which can potentially damage them, but vitamin C helps counteract free radicals.
It strengthens the immune system, and its preventative of colds. It also slows down the progression of any colds, thus making them less harmful. It ensures your immune system is able to fight again bacteria.
It is also good fro asthma sufferers as it acts as an antioxidant in the lungs and air pipes.