Cold sores, small blisters on or around the lips, are a widespread condition. They are often called fever blisters and can cause discomfort. This article explores their viral origin and the role genetics may play in their manifestation.
What Causes Cold Sores
Cold sores are caused by the herpes simplex virus type 1 (HSV-1), a prevalent and contagious virus. While HSV-2 is generally associated with genital herpes, either type can cause sores in oral or genital areas. Once contracted, HSV-1 remains in the body for life, establishing a dormant or latent infection.
The virus resides in nerve cells, specifically the trigeminal ganglia. During this latent phase, the virus is inactive and causes no symptoms. However, various internal or external factors can trigger reactivation, causing it to travel along nerve pathways to the skin’s surface and result in an outbreak.
HSV-1 is widespread globally; an estimated 3.8 billion people under 50 had the infection in 2020. In the U.S., prevalence among individuals aged 14–49 was 47.8% during 2015–2016. Many infected individuals never develop symptoms.
Understanding the Genetic Link
While the herpes simplex virus itself is not inherited, research indicates genetic factors can influence an individual’s susceptibility to HSV-1 infection or the frequency and severity of outbreaks. Genetics do not pass on the virus, but affect the body’s immune response. Certain genetic variations impact how effectively the immune system controls the latent virus and prevents reactivation.
Studies have identified specific genes, such as “Cold Sore Susceptibility Gene-1” (CSSG-1 or C21orf91), that influence vulnerability to frequent cold sores. Different forms of this gene are associated with protection from or increased likelihood of more frequent and severe episodes. Another gene, IL28b, has also been linked to cold sore frequency, with mutations potentially leading to a less adequate immune response.
If cold sores seem to “run in the family,” it is often due to a shared genetic predisposition affecting the immune system’s handling of the virus, rather than direct inheritance of the virus itself. This genetic influence explains why some people experience recurrent outbreaks, while others, despite being infected, never develop symptoms.
How Cold Sores are Transmitted
Cold sores are contagious and spread primarily through direct person-to-person contact. The most common method is skin-to-skin contact, such as kissing, especially when an infected individual has active blisters. Fluid-filled blisters contain a high concentration of the virus, making them infectious.
Transmission can also occur through sharing personal items that have contacted the virus, such as eating utensils, razors, towels, or drinking glasses. Even without visible sores, the virus can be shed from the skin (asymptomatic shedding), though transmission is less likely during these periods.
HSV-1 can also be transmitted from the mouth to other body parts, including the genitals, through direct contact like oral sex, leading to genital herpes caused by HSV-1.
Managing and Preventing Outbreaks
While there is no cure for HSV-1, strategies can help manage symptoms, reduce outbreak frequency, and minimize transmission. Identifying and avoiding personal triggers is key. Common triggers include stress, strong sunlight or wind, fever, other infections, and hormonal changes like menstruation.
Over-the-counter creams like docosanol can shorten healing time if applied at the first sign of tingling. Prescription antiviral medications, such as acyclovir, valacyclovir, and famciclovir, are also effective. These medications interfere with viral replication and can be taken orally to reduce outbreak severity, duration, or prevent future ones.
Practicing good hygiene prevents spreading the virus. This includes washing hands thoroughly after touching a cold sore, avoiding kissing, and not sharing personal items like lip balm, utensils, or towels, especially during an active outbreak. For frequent or severe outbreaks, consult a healthcare provider for a management plan, including daily suppressive antiviral therapy.