What causes enlarged lymph nodes in children?

Presence of a few, small (<0.5 cm) lymph nodes in the neck is normal in children. These are painless. However, it is important to be sure that the child does not have lymph nodes in other parts of the body, the important areas being under-arms, groin, elbow. Also, if the lymph nodes show an increase in size, or number or if child has other symptoms like fever, weight loss, lack of appetite etc, he needs to be evaluated.