When does a cold sore stop being contagious? 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They develop in response to a common viral infection. Generally, a cold sore is contagious for around 15 days. The first sign of a developing cold sore tends to be a burning or tingling sensation in the area. This may be 1–2 days before the onset of visible blisters. Even before it breaks out, it may already be transmissible. The cold sore will appear as a cluster of blisters on the surface of the skin. Typically, these blisters will burst, resulting in an open and painful sore. A scab then forms over the wound. The entire process usually takes around 7–12 days, though the cold sores may last for up to 15 days. In this article, we explore how people contract and transmit the cold sore virus. We also provide information on cold sore symptoms, prevention tips, and treatment options. Transmission Share on PinterestTatiana Maksimova/Getty ImagesThe herpes simplex virus type 1 (HSV-1) is what causes cold sores. According to the National Institutes of Health (NIH), more than 50% of people in the United States have contracted HSV-1 by the time they reach their 20s. Most people contract it during childhood. HSV-1 is highly contagious. People can transmit it to another person by kissing or sharing utensils, towels, or other personal care items. The virus can then enter the body through a small cut in the skin. Once a person has HSV-1 in their system, it is there for life, as there is currently no cure. The virus can remain dormant for long periods but may reactivate at any point. In some cases, however, the virus may never become active. Many people with the virus do not develop cold sores. A person can transmit HSV-1 to others when the virus is inactive. However, a person is much more likely to pass on HSV-1 when cold sores are present. Cold sore triggers Many triggers can cause the virus to reactivate. They may include:dental workemotional distressfeverhormonal changes, such as from menstruationinfectioninjurystressexposure to sunlightsurgery People who develop cold sores may experience them less frequently as they age. According to the American Academy of Dermatology, HSV-1 tends to reactivate less often in people over 35. Reactivation also tends to be more common in the first year after the initial outbreak. Signs of a new outbreak Most people contract HSV-1 during childhood. However, some contract the virus later in life. When someone initially gets the virus, they may experience the following symptoms:a burning sensation before the appearance of painful mouth soresaches and painsfeverflu-like symptomsheadachenauseasore throatswollen lymph nodes Symptoms typically last for up to 2 weeks, though some people may not develop any symptoms at all. Reactivation symptoms and stages Many people experience a burning, itching, or tingling sensation on or around the lips 1–2 days before a cold sore appears. This is called the prodrome stage. During the next stage, fluid filled blisters will develop. Around a third of people experience cold sores at the same location each time. Within 48 hours, the blisters tend to burst and leak fluid. This stage can be painful and may last for around 3 days. This is when the cold sores may be most contagious. In the final stage, a scab forms over the wound. The scab may crack or bleed until it finally clears up. Once the skin is clear of the cold sore, it is no longer possible to transmit it to someone else. Treatment Most cold sore outbreaks do not require a visit to the doctor. They typically clear up on their own within 7–12 days. Trying home treatments during this time can reduce discomfort. They can also prevent transmission to other parts of the body and other people. Home remedies Some home remedies include:Trying topical antiviral medications: Some antiviral cold sore medications, such as docosanol (Abreva), are available over the counter.Applying sunscreen: Protecting cold sores from the sun helps prevent further skin damage. Ideally, people should apply a lip balm with a sun protection factor (SPF) of 30 or higher.Taking pain relief medications: Taking over-the-counter pain relievers, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol), may reduce discomfort.Applying ice: Applying an ice pack to the area may help bring down pain and swelling. People should wrap ice packs in a clean towel first. Applying ice directly to the skin can cause more damage.Trying petroleum jelly: Applying this to cold sores may aid the healing process.Making dietary changes: Eating acidic, salty, and spicy foods can cause burning pain if they touch the sores. Therefore, it can be helpful to avoid these foods until the sores heal. Medical treatments People should see their doctor if cold sores are severe or persist beyond 15 days. A doctor may recommend:prescription antiviral medication in the form of topical cream or oral medicationintravenous antiviral medications (for severe outbreaks)pain relief medications People who experience regular outbreaks may need to take prescription medication to keep their symptoms under control. A person should also see a doctor for cold sore treatment if they:develop numerous soresdevelop sores near the eyes or on the hands or genitalsexperience severe pain with the soresare pregnanthave atopic dermatitishave cancer and are undergoing chemotherapy treatmenthave HIV, AIDS, or another condition that weakens the immune systemtake an immunosuppressant medication In these cases, the cold sores may not go away on their own. Medical treatment can also help prevent complications. Prevention tips The following tips can help limit the spread of HSV-1:Avoid kissing other people while the sores are active.Avoid engaging in oral sex and any other intimate contact while the sores are active.Do not share personal care products, such as razors, lip balms, and towels, with other people.Do not share utensils, drinks, or foods.Refrain from touching the sores unless necessary, such as when applying cream. Wash the hands immediately after touching a cold sore and regularly throughout the day. When cold sores are present, people should take extra precautions during contact with people who have weaker immune systems. This includes children and newborn babies, whose immune systems have had less time to develop. People can also take measures to reduce their chance of experiencing a cold sore outbreak. These include:wearing sunscreen or lip balm with an SPF of 30+ every daypracticing yoga or meditation to help reduce stressgetting enough sleep each nighttaking any prescribed antiviral medications at the first sign of an outbreak Outlook There is currently no cure for cold sores. This means that once a person contracts HSV-1, they will have it for life. However, not everyone who has the virus will develop cold sores. People who are prone to cold sores can try to reduce their exposure to potential triggers. These include stress, sunlight, and infections. Taking prescription medication may be helpful for those who experience regular outbreaks. Summary HSV-1, the virus that causes cold sores, is very common among adults in the U.S. Most people who have it contract the virus in childhood. Cold sores are highly contagious from the time the first symptom appears. This is usually 1–2 days before the sore becomes visible. The virus can remain contagious for up to 15 days. During an outbreak, people should be careful not to transmit the virus to others. Trying home remedies can help relieve the symptoms. If these are not effective, medical treatments can reduce pain and speed up healing. Those who have concerns about cold sores or other mouth lesions should see their doctor. Last medically reviewed on September 12, 2022DermatologyInfectious Diseases / Bacteria / Viruses 5 sourcescollapsedMedical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.Cold sores. (2020).https://www.nhs.uk/conditions/cold-sores/Cold sores: Diagnosis & treatment. (n.d.).https://www.aad.org/public/diseases/a-z/cold-sores-treatmentEbert Brand, J. (2011). Common sense about cold sores.https://www.myamericannurse.com/common-sense-about-cold-sores/National Institutes of Health. (2008). Learning how cold sore viruses hide [Press release].https://www.nih.gov/news-events/nih-research-matters/learning-how-cold-sore-viruses-hideOral herpes. (n.d.).https://www.hopkinsmedicine.org/health/conditions-and-diseases/herpes-hsv1-and-hsv2/oral-herpesFEEDBACK:Medically reviewed by Avi Varma, MD, MPH, AAHIVS, FAAFP — By Jayne Leonard — Updated on September 12, 2022 Latest newsWhat sets 'SuperAgers' apart? Their unusually large neuronsOmega-3 may provide a brain boost for people in midlifeSeasonal affective disorder (SAD): How to beat it this fall and winterCDC: Monkeypox in the US 'unlikely to be eliminated in the near future'Why are more women prone to Alzheimer's? 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