Mouth herpes{also known as oral herpes) primarily affects children of more than 6 months of age or who are aged 1-2 years  and it affects adults also.  When this virus is inside your mouth it is sometimes confused with a canker sore. It results in painful red fluid-filled blisters or lesions on the tongue, lips, inside of the cheeks, and gums often accompanied with an itchy or burning sensation. Muscle pain and fever can also be suffered at a later stage.  If treatment is ignored, a herpes infection inside your mouth can be dangerous.
Oral herpes is also known commonly as cold sores and fever blisters but is different entity from oral canker sores although canker sores may sometimes be associated with HSV infection. Canker sores occur solely inside the mouth. Oral herpes occurs inside and around the mouth. Most of the time HSV-1 causes mouth symptoms and in a minority of cases it may also be responsible for genital symptoms. The opposite is true for HSV-2 – it causes genital symptoms in the majority of cases while only a few cases of HSV-2 infection will result in mouth symptoms. HSV-1 infection may be seen in all ages, including children, but when genital herpes is seen in children, sexual abuse needs to be a consideration.
Herpes virus type 5 is also known as cytomegalovirus. It is the major cause of mononucleosis. Mononucleosis causes symptoms similar to infectious mononucleosis. It is spread via blood transfusion, breast-feeding, organ transplants, and sexual contact. The virus causes diarrhea, or severe vision problems and even leads to AIDS. People with weakened immune systems are more susceptible to these diseases.

Condoms offer moderate protection against HSV-2 in both men and women, with consistent condom users having a 30%-lower risk of HSV-2 acquisition compared with those who never use condoms.[49] A female condom can provide greater protection than the male condom, as it covers the labia.[50] The virus cannot pass through a synthetic condom, but a male condom's effectiveness is limited[51] because herpes ulcers may appear on areas not covered by it. Neither type of condom prevents contact with the scrotum, anus, buttocks, or upper thighs, areas that may come in contact with ulcers or genital secretions during sexual activity. Protection against herpes simplex depends on the site of the ulcer; therefore, if ulcers appear on areas not covered by condoms, abstaining from sexual activity until the ulcers are fully healed is one way to limit risk of transmission.[52] The risk is not eliminated, however, as viral shedding capable of transmitting infection may still occur while the infected partner is asymptomatic.[53] The use of condoms or dental dams also limits the transmission of herpes from the genitals of one partner to the mouth of the other (or vice versa) during oral sex. When one partner has a herpes simplex infection and the other does not, the use of antiviral medication, such as valaciclovir, in conjunction with a condom, further decreases the chances of transmission to the uninfected partner.[14] Topical microbicides that contain chemicals that directly inactivate the virus and block viral entry are being investigated.[14]
The most effective method of avoiding genital infections is by avoiding vaginal, oral, and anal sex.[1] Condom use decreases the risk.[1] Daily antiviral medication taken by someone who has the infection can also reduce spread.[1] There is no available vaccine[1] and once infected, there is no cure.[1] Paracetamol (acetaminophen) and topical lidocaine may be used to help with the symptoms.[2] Treatments with antiviral medication such as aciclovir or valaciclovir can lessen the severity of symptomatic episodes.[1][2]

"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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