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Cold Sores (Oral HSV-1): Symptoms, Treatment and Transmission
Cold sores are usually caused by oral HSV-1. Learn what symptoms to expect, when antivirals may help and how to reduce transmission risk.
MEDICAL & WELLNESS
Brandon
1/10/20264 min read
Cold Sores Are Usually Oral HSV-1
Cold sores are blisters or ulcers on or around the lips that are usually caused by herpes simplex virus type 1 (HSV-1). HSV-1 is extremely common: the World Health Organization estimates that 3.8 billion people under 50—about 64% of that age group—had HSV-1 infection globally in 2020.
Many people never notice symptoms. When symptoms do occur, the virus can become inactive and later reactivate. A cold sore does not mean that someone has recently acquired HSV or that a partner has been unfaithful.
What a Cold Sore Can Look and Feel Like
A recurrent cold sore may begin with tingling, itching, burning or tenderness. Small blisters can then appear, break open, form a crust and heal. Some episodes are milder and never follow every stage.
There is no reliable day-by-day timetable. The NHS says cold sores should begin to heal within about 10 days, but the exact course varies. A first recognised episode can be more extensive and may include fever, swollen glands or painful gums and sores inside the mouth.
Not every lip lesion is HSV. Mouth ulcers, spots, impetigo, allergic reactions and other conditions can look similar. A pharmacist, GP or sexual-health clinician can help if you are uncertain.
How Oral HSV-1 Spreads
HSV-1 mainly spreads through direct contact with virus in a sore, saliva or skin around the mouth. It can sometimes spread when the skin looks normal, although the risk is greatest when an active cold sore is present.
Oral HSV-1 can also be passed to a partner’s genitals during oral sex. While you have tingling or a visible sore:
Avoid kissing and oral sex until the skin has completely healed.
Do not kiss a newborn baby; neonatal herpes can be very serious.
Wash your hands with soap and water after touching the area or applying treatment.
Avoid sharing lip balm, razors or other items that have directly touched the sore or saliva.
Avoid touching your eyes after touching the sore.
Ordinary contact such as working, exercising or sharing the same room does not spread HSV. There is no need to isolate yourself. For more detail, read our HSV transmission guide.
Cold Sore Treatment
Cold sores usually heal without treatment. Treatment may ease discomfort or shorten an episode, particularly when started promptly, but it does not remove HSV from the body and cannot guarantee that a blister will be prevented.
Self-care and pharmacy options
Use paracetamol or ibuprofen if these are safe for you and follow the packet instructions.
Drink enough fluid and choose cool, soft foods if eating is uncomfortable.
Ask a pharmacist about antiviral cream, cold-sore patches or pain-relieving products.
If using aciclovir cream, follow the product instructions and wash your hands before and after applying it. NHS guidance says it should be started when tingling or itching begins.
Do not pick the sore or peel the crust.
A 2017 systematic review found that nucleoside antiviral medicines shortened healing by an average of less than one day across the included trials, although results varied by treatment and study. This is useful but more modest than claims that antivirals dramatically shorten every episode.
Prescription antiviral tablets
A GP may consider antiviral tablets when cold sores are very large, painful, frequent or particularly disruptive, or when a person has a weakened immune system. The appropriate medicine, dose and timing depend on your health, kidney function, other medicines and the exact diagnosis.
Do not copy an online dosing schedule, use someone else’s tablets or convert between aciclovir and valaciclovir yourself. Our aciclovir and valaciclovir comparison explains the differences without replacing a prescription.
Can You Prevent Recurrences?
Cold sores may recur after illness, strong sunlight, injury, stress or other changes, but triggers differ and an episode can occur without an obvious cause. Tracking your own pattern may be more useful than following a universal trigger list.
If sunlight reliably triggers outbreaks, consider an SPF lip balm and shade. If episodes are frequent or severe, discuss whether prescription suppressive treatment is appropriate rather than starting a long-term regimen yourself.
Evidence does not support presenting daily lysine as a proven prevention plan. A Cochrane review found no evidence that lysine prevented recurrent cold sores, and a separate evidence review concluded that controlled studies were still needed. Restrictive “high-lysine, low-arginine” diets are therefore not a standard cold-sore treatment.
Evidence for lemon balm, propolis, tea tree oil and other complementary products is limited or inconsistent. “Natural” does not automatically mean effective or irritation-free, particularly on broken skin.
When to Get Medical Advice
Speak with a pharmacist or GP if:
The cold sore has not started to heal within 10 days.
It is very large, unusually painful, keeps returning or affects eating and drinking.
You have swollen, painful gums and sores inside the mouth.
You are unsure that the lesion is a cold sore.
You are pregnant or have a weakened immune system, including because of chemotherapy, advanced HIV, an organ transplant or immune-suppressing medicine.
Seek urgent medical advice for a painful red eye, light sensitivity, blurred vision or a sore close to the eye. HSV infection of the eye can threaten sight and needs prompt assessment. Use NHS 111 if you need urgent guidance; call 999 or go to A&E for a life-threatening emergency.
Common Questions
Can a cold sore cause genital herpes?
Yes. Oral HSV-1 can spread to the genital area through oral sex. Avoid oral sex from the first warning symptoms until the sore has completely healed.
Am I only contagious when a blister is open?
No. Transmission can occur from the first tingling or burning sensation until healing is complete, and HSV can occasionally spread without visible symptoms. Active sores carry the greatest risk.
Will a cold sore always heal in 10 days?
No. Many begin healing within that period, but timing varies. Seek advice if it has not started to heal after 10 days or is severe.
Should I take lysine every day?
Current evidence does not establish a standard effective lysine dose for preventing or treating cold sores. Ask a clinician or pharmacist before using supplements, particularly if you have other health conditions or take medicines.
Can I shave or exercise?
You can exercise if you otherwise feel well. Take care when shaving around the lesion, do not share razors and wash your hands if you touch the area. Shared gym equipment is not considered a typical route of HSV transmission.
Can cold sores be cured?
No treatment removes HSV from the body. Medicines can reduce symptoms or shorten some episodes, and many people experience fewer recurrences over time.
Sources and Further Reading
Last reviewed: 5 October 2026. Written by Brandon Hart. This article has not been medically reviewed and is for general education, not diagnosis or personalised treatment advice.
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