Eat plenty of whole grains, pulses and nuts for B vitamins which help to maintain a healthy immune system and fresh fruit and vegetables to ensure a good intake of vitamin C. citrus fruits, grapes, and black berries are particularly useful because they also contain bioflavonoids which act with vitamin C to keep the blood capillaries healthy.

Bioflavonoids also have anti-inflammatory properties. Vitamin E, which is found in nuts, sunflower seeds, seed oils and avocados, also supports the immune system. Eating natural decongestants may be helpful. They include raw or cooked onions and garlic, and herbs and spices such as ginger, thyme, elderflower, horseradish, cloves and cinnamon.