context: Your immune system helps guard your body from germs, viruses, and other threats. What you do every day can help, or hamper, your immune system. What works and what doesn't? How can you keep your immune system in top shape? Let's separate myth from fact. Ongoing stress, such as being in a difficult relationship, living with a chronic disease, or being a caregiver, can take its toll on your immune system. Over time, it can make you more vulnerable to illnesses, from colds and flu to chronic diseases such as diabetes and heart disease. Chronic stress seems to age the immune system, studies show, making you more likely to get a cold or the flu, and to develop diabetes and heart disease. Everyone goes through stress. What matters is how you handle it. Getting better at managing stress can help. Even something as simple as deep breathing can lessen the effects of stress. Or try other relaxation techniques, such as: Meditation Yoga Other types of exercise Counseling can make a big difference, too. Totally untrue. Getting a flu vaccine prepares your immune system for the flu. A flu vaccine teaches your immune system to recognize that virus as a threat. While some people may still get the flu after having a flu shot, they'll probably have a milder form of the illness. That's because antibodies made in response to the vaccine can still provide some protection. So why do some people swear a flu vaccine gave them the flu? Some may mistake the occasional, short-lived side effects of the vaccine (slight fever, aches) for flu symptoms. And the time of year people are most likely to get the vaccine is when colds and other respiratory illnesses are common. If you get the vaccine and then get sick with an unrelated bug, you may assume, incorrectly, that the vaccine caused the illness. While no single food will upgrade your immune system, poor nutrition can have a negative effect on the immune system. What counts is having a balanced diet. Just about everyone could stand to eat more fruits and vegetables. They're rich in vitamins and minerals that are good for you. If you're thinking about getting supplements to cover your nutritional needs, check with your doctor or a dietitian. Chances are, you're getting what you need from food, unless you're on a strict diet, are pregnant, or have certain medical conditions. As you age, your body has a harder time fighting off infections. Older adults are more likely to get sick from infections. And those infections, especially flu and pneumonia, are more likely to be fatal, compared with younger people. Why it happens isn't clear. It may be about your immune system slowing down. Or it could be partly linked to nutrition, since seniors often eat less and don't always get the nutrients they need to keep their immune systems strong. So eat lots of fruits and vegetables. They're good for you at any age. A fever can help your immune system fight infections in two ways. A higher temperature in the body speeds up the functioning of cells, including the ones that fight illness. They can respond to invading germs faster. Also, higher body temperatures make it harder for bacteria and viruses to thrive in the body. If you've had a fever for more than several days, a high fever, or if you have fever and other symptoms like severe vomiting, diarrhea, earache, or cough, call your doctor. Always call a doctor for any fever in infants three months of age or younger. Also see your doctor if a child under age 3 has a fever above 102 F or if they have a fever for more than a day or two. People with a suppressed immune system, such as those with HIV, those who've had an organ transplant, those who are taking chemotherapy, or those who have any other medical conditions such as diabetes and heart disease, should also give the doctor a call. Allergy symptoms happen when your immune system reacts to something harmless, like pollen, pet dander, or mold. Your body sees the allergen as an invader and attacks it, giving you a runny nose and itchy eyes. People can inherit a tendency toward allergies; if you have allergies, your children have a greater chance of also having allergies, although they may be allergic to different things. Allergies are treated by avoiding your allergy triggers and taking medication to control symptoms. For some people, allergy shots may be an option. Over a period of time, usually several years, allergy shots may help your immune system get used to the allergen, so that it doesn't produce the bothersome allergy symptoms.