Could you tell me what are possible leads to of swollen lymph nodes?

Many causes: Infections of the skin or mucosa(in the throat) are the commonest cause. But such nodes are tender and will regress in size once the infection has resolved in 2-4 weeks. If the nodes are painless and are increasing in size, then they need to be checked by a physician. If their size is less than 1-centimeter and has not increased during the last one year, then they are not likely to be serious prob.