Lymph nodes are one of the passageways that our body uses to channel out toxins.
When we've been killing organisms or have bee fighting down infections, our Lymph nodes, where are located throughout the body, can become clogged.
For the neck, I have had great success following this manual draining massage feature. It begins working quite soon, and it is not necessary to do 50 reps.
/youtu.be/QA-wi0d7-RoIt might not be what your problem is, but it's free and worth a try. Wouldn't hurt.