Can severe allergies cause lymph nodes to swell. One is 1.75 cm. Cervicle. On coroided artery. Been there 2 yrs.?

Monitoring Centers. Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.
Lymph node & allergy. No. Generally allergies do not cause reactions in your lymph nodes with the expception of certain rare hypersensitivity reactions. Usually i would not be concerned about a gland < 1 inch in diameter, especially if it is not growing in size and does not hurt.