What are the most common things that causes persistant lymohoadenaoathy throughout entire neck. in 17 yr old male. 1cm-1.75 cm. all of them. ?

Infection/Hodgkin: Lymphadenopathy can occur after infections such as mononucleosis (mono), or with hodgkin lymphoma in this age group. If the enlarged lymph nodes last more than 4-6 weeks, you should be evaluated by a health care provider.

Lymph nodes: The most common cause of lymph node enlargement in the neck in a 17 year old is a viral illness. Large lymph nodes, which are greater than 2 cm in size and persist for weeks are less common. These can be seen with mononucleosis, some drug reactions and other more serious conditions. If the lymph nodes persist for 2 months and the test for mononucleosis is negative a biopsy should be done.

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.