This citrus fruit is a great source of vitamin C, which helps support the immune system. Its specialty is the reduction of colds. The percentage of this vitamin in grapefruit is a whopping 59%. Grapefruit harbours antioxidants that help fight wrinkles and skin ageing. It promotes the production of collagen, which keeps our skin young and fresh. If you have weakened immunity, your mouth is often accompanied by cold sores. Grapefruit is the clear winner in the fight against them. It has also proven itself for chapped lips.