When should I worry about swollen lymph nodes?

Suzanne Berman, M.D.

What are lymph nodes?

Lymph nodes are like your body's infection policemen. They are found all over the body, looking for any sign of infection that they can "arrest." Each set of lymph nodes has its own "beat" that it monitors. For example:

Lymph nodes in the sides of the neck watch over the nose and throat.
Lymph nodes behind the ears and on the back of the neck watch over the scalp skin.
Lymph nodes in the armpits watch over the arms and chest.
Lymph nodes in the groin watch over the legs.

If an infection in one of these body zones occurs, the associated lymph nodes get busy. This causes those lymph nodes to swell up. For example, if you catch a cold virus, which causes an infection in your nose and throat, there may be swelling in the lymph nodes of the neck. They often swell to about the size of a quarter.

So a big lymph node means that there's an infection?

No, not necessarily. (These policemen make a lot of false arrests!) Lymph nodes will swell up when the body suspects there's an infection - even if there's not really one there. Frequently, they swell up when there's irritation of the area when no infection is present.

For example, lymph nodes behind the ears or on the back of the neck will grow in response to an irritation of the scalp, caused by:

a bug bite on the head
a cut or abrasion on the scalp
a fetal scalp monitor during labor
a harsh shampoo
bad eczema, cradle cap, or another skin condition

All of these things are really harmless. But the body isn't sure at first, so it activates those lymph nodes - just to be sure. As a result, you'll feel a small knot - usually the size of a pea or kernel of corn - on the back of your child's neck.

When should I worry about a big lymph node?

Let us check it out in the office if:

if the lymph node is painful to the touch
if the skin over it is hot or red
if there is pus draining from the skin around the lymph node
if the child has other concerning symptoms, like unexplained fever, loss of appetite, weight loss, etc.
if there are lots of big lymph nodes, instead of just one

How long will the big lymph node last?

Sometimes weeks to months. The lymph nodes can swell up quickly, but usually take much longer to resolve.