The causes of reactivation are uncertain, but several potential triggers have been documented. A 2009 study showed the protein VP16 plays a key role in reactivation of the dormant virus. Changes in the immune system during menstruation may play a role in HSV-1 reactivation. Concurrent infections, such as viral upper respiratory tract infection or other febrile diseases, can cause outbreaks. Reactivation due to other infections is the likely source of the historic terms 'cold sore' and 'fever blister'.
Primary orofacial herpes is readily identified by examination of persons with no previous history of lesions and contact with an individual with known HSV infection. The appearance and distribution of sores is typically presents as multiple, round, superficial oral ulcers, accompanied by acute gingivitis. Adults with atypical presentation are more difficult to diagnose. Prodromal symptoms that occur before the appearance of herpetic lesions help differentiate HSV symptoms from the similar symptoms of other disorders, such as allergic stomatitis. When lesions do not appear inside the mouth, primary orofacial herpes is sometimes mistaken for impetigo, a bacterial infection. Common mouth ulcers (aphthous ulcer) also resemble intraoral herpes, but do not present a vesicular stage.
Varicella-zoster is transmitted though the mucosa of the respiratory system, specifically the upper respiratory tract, or the conjunctiva of the eye. Initial replication takes place in the regional lymph nodes, and then the virus spreads and replication begins in the liver and spleen. The virus is then transported to the skin where the rash develops. The incubation period of varicella is about 10 to 21 days.
During stage 1, the virus comes in contact with the skin, enters through cracks or breaks, and reproduces. In this phase, symptoms like fever might occur. The incubation period for oral herpes is between 2 to 12 days. The symptoms last for about 3 weeks. The symptoms may be mild or serious, and occur within the first three weeks after contracting the infection. These symptoms include;
"Oral herpes is an infection found in the mouth, or on and around the lips, caused by the Herpes Simplex Virus (HSV)," Michael explains. "There are two types or strains of this virus called HSV1 and HSV2. Usually, the HSV1 strain infects the mouth and lips, and the HSV2 strain infects the genitals. It is however possible for HSV2 to infect your mouth and lips."