A cold sore, also known as a fever blister, is a small, painful blister or group of blisters that typically appears on or around the lips, although they can also occur on other areas of the face or inside the mouth. These sores are caused by the herpes simplex virus (HSV), most commonly HSV type 1 (HSV-1), although HSV type 2 (HSV-2), which is more often associated with genital herpes, can also cause cold sores.

Cold sores are highly contagious and can be spread through direct contact with the sores or through contact with the saliva of an infected person, even when sores are not present. This is because the virus can be shed from the skin even in the absence of visible symptoms. The initial infection with HSV-1 often occurs in childhood and may or may not cause symptoms. Once a person is infected, the virus remains in the body in a dormant state, residing in nerve cells. Periodically, the virus can reactivate, leading to the development of cold sores.

The reactivation of the virus and subsequent outbreak of cold sores can be triggered by various factors, including stress, fatigue, illness, hormonal changes, exposure to sunlight, or a weakened immune system. The first sign of a cold sore is often a tingling, itching, or burning sensation around the lips or face, followed by the appearance of small, fluid-filled blisters. These blisters eventually break open, ooze, and form a crust before healing completely, typically within two to four weeks.

Cold sores can be painful and may cause discomfort, but they usually heal on their own without leaving scars. However, antiviral medications, such as acyclovir, valacyclovir, or famciclovir, can be prescribed to reduce the severity and duration of an outbreak. Over-the-counter topical treatments may also help alleviate symptoms.

Preventing the spread of cold sores involves avoiding close contact with infected individuals during an outbreak, not sharing personal items like lip balm or utensils, and practicing good hygiene. People with frequent outbreaks may benefit from daily antiviral medication to reduce the frequency of recurrences.

In summary, cold sores are a common viral infection caused by the herpes simplex virus, characterized by painful blisters around the mouth. They are contagious and can be managed with antiviral treatments and preventive measures. Understanding the triggers and symptoms can help individuals manage and reduce the impact of cold sores on their daily lives.

Cold sore (Wikipedia)

Cold sore
Other names	fever blister, herpes labialis, oral herpes, orolabial herpes
A cold sore on the lower lip. Note the blisters in a group marked by an arrow.
Specialty	Infectious disease
Symptoms	Burning pain followed by small blisters or sores
Complications	Herpes encephalitis, herpetic whitlow
Usual onset	< 20 years old
Duration	Heals within 10 days
Causes	Typically herpes simplex virus type 1 (direct contact)
Diagnostic method	Usually based on symptoms
Differential diagnosis	Herpangina, aphthous stomatitis, impetigo, mononucleosis, acne
Prevention	Avoiding exposure, antiviral medication
Treatment	Zinc oxide, anesthetic, or antiviral cream, antivirals by mouth
Prognosis	Good
Frequency	2.5 per 1,000 affected per year

A cold sore is a type of herpes infection caused by the herpes simplex virus that affects primarily the lip. Symptoms typically include a burning pain followed by small blisters or sores. The first attack may also be accompanied by fever, sore throat, and enlarged lymph nodes. The rash usually heals within ten days, but the virus remains dormant in the trigeminal ganglion. The virus may periodically reactivate to create another outbreak of sores in the mouth or lip.

The cause is usually herpes simplex virus type 1 (HSV-1) and occasionally herpes simplex virus type 2 (HSV-2). The infection is typically spread between people by direct non-sexual contact. Attacks can be triggered by sunlight, fever, psychological stress, or a menstrual period. Direct contact with the genitals can result in genital herpes. Diagnosis is usually based on symptoms but can be confirmed with specific testing.

Prevention includes avoiding kissing or using the personal items of a person who is infected. A zinc oxide, anesthetic, or antiviral cream appears to decrease the duration of symptoms by a small amount. Antiviral medications may also decrease the frequency of outbreaks.

About 2.5 per 1000 people are affected with outbreaks in any given year. After one episode about 33% of people develop subsequent episodes. Onset often occurs in those less than 20 years old and 80% develop antibodies for the virus by this age. In those with recurrent outbreaks, these typically happen less than three times a year. The frequency of outbreaks generally decreases over time.