A heavy schedule of exercise, plus the stresses and strains of today’s’ fast pace of life, can take its toll on our health. This can then increase susceptibility to common illnesses. The immune system has evolved to protect us against the many viruses, bacteria and parasites that attack our bodies on a day-to-day basis. This defence mechanism involves many different cell types and chemical messengers and its effectiveness can be influenced by a variety of factors. These include smoking, alcohol consumption, psychological stress, strenuous exercise, nutritional status, age, gut flora and genetics.