I would like to know all about reactive lymphadenites?

Several things!: Lymph node enlargement secondary to draining from its lymphatic drainage area. Can be\ secondary to bacterial and viral infections, or systemic inflammation, as with sle. Will go away when causes is eradicated. Hence the term "reactive lymphadenitis.".

Lymphadenitis: Means inflamed lymph nodes. It is usually a "reaction" to an infection or other inflammatory process. Lymph node enlargement can happen from many causes, one of them being malignancy. So the most important part about "reactive" is that it is not cancer. But, just because it is not cancer, enlarged lymph nodes could be serious, so see your doctor for more information!

Lymphadenitis: Inflammation of a lymph node is called lymphadenitis. In practice, the distinction between lymphadenopathy and lymphadenitis is rarely made. Inflammation of lymph channels is called lymphangitis. Infectious lymphadenitides affecting cervical lymph nodes are often called scrofula (see tuberculous cervical lymphadenitis).