Chronic stress raises cortisol levels, which can slow down how well your body fights off infections. Knowing how cortisol affects your immune system helps you understand how long-term stress hurts your health. Too much cortisol from ongoing stress can make your immune system weaker and make you more likely to get sick. Learn how to naturally control cortisol and boost your body's ability to stay healthy by keeping a balanced lifestyle, getting enough rest, and eating well.