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Cold, Flu, & Cough Health Center

Myths and Facts About Your Immune System

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Fact: Your immune system probably gets weaker as you grow older.

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.

Myth: Running a fever when you're sick weakens your immune system.

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, or if you have fever and other symptoms like severe vomitingdiarrhea, earache or cough, call your doctor.

Always call a doctor for  fever in infants three months of age or younger.  Also see your doctor if a child under age 2 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.

Fact: Seasonal allergies are caused by an abnormal response by the immune system.

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.

WebMD Medical Reference

Reviewed by Melinda Ratini, DO, MS on November 02, 2015

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