Exterior syndrome and interior syndrome should be distinguished from each other in the syndrome differentiation of epidemic parotitis. The symptoms of exterior syndrome of epidemic parotitis include no fever or slight fever at the early stage, concurrent chills, parotidean swelling and distension, uncomfortable mastication with pain worsened when the mouth is open, and soft diffuse swelling on one side or two without clear border. The interior syndrome of epidemic parotitis is mostly caused by virulent heat pathogen transmitted interiorly from the exterior, or internal accumulation of excessive exogenous toxin. Therefore, the symptoms include high fever without abatement, headache, vomiting, thirst with the inclination to drink, hard parotidean swelling and distension and difficult mastication.

Because of excessive toxin and heat, healthy qi fails to defeat pathogenic factors during the struggle between the two. In this case, heat and toxin sink in the heart and liver while excessive heat causes wind. Then the symptoms are high fever without abatement, headache, stiff nape, even clonic convulsion, coma, etc.. If heat and toxin involve the testis and abdomen, pain of one side or both sides of lower abdomen, or swelling and pain of the testis will occur, accompanied by fever, vomiting, etc. in most cases.