Rosehips are tiny red fruit that grows on rose plants. Rose hips are the best source of vitamin C, they contain 50% more vitamin C than oranges. Because of the high vitamin C content they are an excellent immune system booster, and are often used as a supplement to prevent or treat a cold. The vitamin A is also beneficial to the immune system. It can help to prevent infections from both bacteria and viruses. It helps the immune system to fight off any infections that do occur too.