The Weird Sign You’re Getting Sick

Are you aware of this sneaky sign that your body is fighting off an infection? (Photo: Getty Images)

When you have a bump or lump beneath the skin, your mind probably jumps to assume it’s either benign — like an itchy bug bite — or very serious — like cancer. But here’s something you may not have realized: That lump could actually be a swollen lymph node, an indicator that your body is fighting off an infection.

Many people are aware that swollen lymph nodes under the chin are a sign of sickness, but most don’t realize that those aren’t the only lymph nodes a person has. It’s understandable, then, that you might be a little concerned if you stumble across a swollen lymph node in a place you weren’t expecting — say, your arm or genitals.

In fact, “we have more than 500 lymph nodes located all over the body,” says Baltimore-area primary care physician Kathryn Boling, MD. “Some are deep within the body and cannot be felt; others — like those down the inside of the arm, in the neck, and in the groin — can be more easily felt.”

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To understand why lymph nodes swell up, it’s important to understand how they work in the first place. Think of your lymph nodes as a filtration system, says Boling: They’re connected by a chain through which lymph fluid-containing immune cells flow.

When you’re sick, invading microbes will be brought to the immune cells within your lymph nodes to be destroyed, explains board-certified infectious disease specialist Amesh A. Adalja, MD, an assistant professor at the University of Pittsburgh Medical Center. The presence of the microbes causes your immune cells to multiply as part of the immune response, and that makes your lymph nodes puff up. When the microbes are obliterated, the swelling in your lymph nodes will go down. 

While your lymph nodes can swell when your body is fighting cancer, “the most common cause of lymph node swelling is an infection,” says Terri Richardson, MD, an internist with Kaiser Permanente in Colorado.

You won’t typically notice a lymph node if it’s not infected, but it’s about the size and shape of a small lima bean in its normal state, says Boling. When a lymph node is swollen, you’ll usually feel a bump that can be as small as the size of a pea, but can get much larger. That bump may be soft or spongy, and sometimes it will feel a little painful or tender to the touch. Richardson says your lymph node can even look a little red, like a pimple.

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The location of swollen lymph nodes isn’t random: It’s directly linked to where your body is fighting an infection. “Each lymph node is tasked with responding to a specific anatomical site,” says Adalja. So, for example, a swollen lymph node in your neck may indicate that you have strep throat, while one in your armpit can be a sign that you have an infection in your arm or chest. Swollen lymph nodes below the belt could be an indicator of a genital issue, like a yeast infection.

While lymph nodes typically swell up when you’re sick, it’s also possible to have a swollen lymph node without feeling any symptoms. “Sometimes just being exposed to a virus and not even feeling very ill can cause lymph nodes to enlarge as the body fights off the infection,” says Boling. If your lymph nodes do their job quickly, you may never even notice you were fighting something off in the first place.

Since the lymph node response is a normal function of the body, you don’t need to rush to your doctor every time you notice a bump — especially if it goes away within two to four weeks. However, you should see your doctor if the bump is firm, feels rubbery or rock hard, and doesn’t go away within a month.

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