Talk to Ent Specialist on Swollen Lymph Nodes

My sister has had swollen lymph nodes for several years. We have a family history of tonsil issues—she had hers removed—and seasonal and general allergies, which seem to be genetic. While she is generally fine, she experiences frequent allergies. The lymph nodes are not painful and appear to be the same size on both sides of her throat. I'm now growing concerned about her health. I’d appreciate it if someone could help me understand what these might be, and which specialist we should consult.