Most Lymph nodes swelling is from infections;
Most generalised lymphadenopathy is due to benign self-limited disease, such as viral or bacterial infection but it can be caused by a wide range of conditions;
Causes
Generalised lymphadenopathy may be caused by a wide range of conditions, as follows:
Viral
Common upper respiratory infections
Infectious mononucleosis, cytomegalovirus (CMV)
Rubella, varicella, measles
HIV
Hepatitis A and hepatitis B
Roseola infantum - human herpesvirus type 6 (HHV-6)
Dengue fever
Adenovirus
Bacterial
Septicaemia
Typhoid fever
TB
Syphilis
Plague
Lyme disease
Tularaemia
Brucellosis
Protozoal
Toxoplasmosis, leishmaniasis, Chagas' disease
African trypanosomiasis (sleeping sickness)
Fungal
For example, coccidioidomycosis
Autoimmune disorders and hypersensitivity states
Juvenile idiopathic arthritis
Systemic lupus erythematosus (SLE)
Drug reactions (eg, phenytoin, allopurinol, primidone)
Serum sickness