It should not be confused with conditions caused by other viruses in the herpesviridae family such as herpes zoster, which is caused by varicella zoster virus. The differential diagnosis includes hand, foot and mouth disease due to similar lesions on the skin. Lymphangioma circumscriptum and dermatitis herpetiformis may also have a similar appearance.
The herpes virus is probably the most well-known virus after influenza (the flu) or the common cold. What most people don’t know is that this nasty little virus can take several different forms, eight to be exact. The most common form of the herpes virus is chicken pox, which is called varicella-zoster. Herpes simplex is the sexually transmitted version of the virus.
The flares are caused when your immune system falters. This can be due to a number of reasons. Anything from daily stressors, lack of sleep, poor nutrition, weight gain, concurrent illnesses etc may cause your immune system to be distracted from the Herpes Simplex Virus (HSV) infection. The moment that happens, the virus will flare resulting in rashes, cold sores, ulcers or blisters on your body.
Herpes virus type 1 (HSV-1) is the cause of cold sores or fever blisters around the mouth. Usually, the sores or blisters can show up on the outside of the mouth or on the lips. But sometimes, they can be inside the mouth, on the face, nose, cheeks or fingers. HSV-1 can also lead to infection of the genitals, called genital herpes. This occurs when you have a cold sore and perform oral sex on another person. HSV-1 infections are highly contagious. Apart from oral-genital contact, they can be spread through skin-to-skin contact. If you come into contact with a person or a thing that carries HSV-1, you will be likely to get it, too. Often, people get HSV-1 from kissing someone with a cold sore or when they share eating utensils, razors, or towels.
Herpes symptoms commonly show in or around the mouth. Sores may also occur at the back of the throat, causing the lymph nodes in the neck to swell. Mouth herpes is very common in children, as their parents or relatives can pass it on to them easily by a greeting or goodnight kiss. To get a better understanding of oral herpes, let us take a look at its causes.

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.[71] Changes in the immune system during menstruation may play a role in HSV-1 reactivation.[72][73] 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'.
"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."
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