My son now 6 year old having swollen lymph nodes since his 6 month. Shown to many pediatricians and told not an issue. This lymph nodes remain unchanged in size and number in both sides of necks.he is allergic and asthmatic.This lymph nodes is slippery and movable. Is there any underlying cause. Is there anything to worry . Sometimes it become little small sometimes little big  . But almost remain unchanged .