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What Causes Cold Sores? The Ultimate Guide

A woman applies cream to a cold sore on her lip while looking in a mirror.


At first, you may not have known what the tingling, burning sensation on your lip was. But then the tiny, fluid-filled blisters erupted around your mouth — and you knew you had a cold sore.

Many people suffer from cold sores all their lives, and some only experience them in adulthood.

But what causes cold sores? Where do they come from?

What Causes Cold Sores?

Herpes simplex virus, type 1 (HSV-1), is most often responsible for cold sores, also called oral herpes. HSV-1 is an extremely common virus, and it spreads easily.

Once infection occurs, the first outbreak of cold sores can take several weeks to appear. After the initial outbreak, the herpes virus retreats into a dormant state in the nerves around the mouth. But when triggered by certain stressors, the herpes virus reactivates to cause additional cold sore outbreaks.

It's important to note that having HSV-1 does not mean that a person will develop genital herpes. Genital herpes is a separate infection and is usually caused by the herpes simplex virus, type 2 (HSV-2), rather than type 1.


How Does the Virus That Causes Cold Sores Spread?

HSV-1 spreads through close contact with someone who is already infected with the virus, especially when a cold sore is present.

Cold sores are contagious from the first tingle or burning sensation on the lips. Sores remain contagious the entire time they're present, and they're most contagious when they burst and release their fluid. The cold sore virus can even infect others when no sores are present through a phenomenon called asymptomatic shedding.

Anyone can get HSV-1. For example, infants and children often contract HSV-1 through close contact with an infected family member.

Here are a few other ways HSV-1 commonly spreads.


Kissing someone with a cold sore is one of the most common ways HSV-1 spreads. Even receiving a kiss on the cheek from them could lead to infection. Cold sores are always contagious, so it's never safe to kiss someone until after a cold sore has completely healed.

Mucous Membranes

HSV-1 can easily spread through touching mucous membranes (mouth, eyes, or genitals) after contact with a cold sore. This is one reason it's important to wash your hands after you touch your own cold sore.

Oral Sex

While HSV-1 is not considered a sexually transmitted infection, it's important to know that the virus is transmissible during oral sex. If you or your partner have an active cold sore outbreak, it's best to refrain from such intimate contact until the cold sore heals.

Sharing Cups, Straws, and Personal Care Products

Although the HSV-1 virus can only live outside the human body for a few hours, sharing a lipstick, lip balm, drink, or straw with someone with a cold sore could still spread the virus and should be avoided. Sharing a facial razor could also transmit HSV-1 by allowing cold sore fluid to pass from one user to the next.

What Causes Cold Sores To Come Back?

After the initial cold sore infection, HSV-1 remains in your body for the rest of your life. Most of the time you won't experience any symptoms, but sometimes the virus will flare up and cause new cold sores to erupt.

Several known triggers can bring on further cold sore outbreaks.

What Causes Cold Sores? The Ultimate Guide Infographic

Dietary Choices

Certain foods can contribute to recurring cold sore outbreaks:

  • Foods rich in L-arginine, such as beans, nuts, sunflower seeds, and poultry.
  • Processed foods such as frozen meals or sugary breakfast cereals.
  • Highly acidic foods like citrus fruits, tomatoes, and soda.
  • Spicy foods.

Poor dietary choices in general, such as a diet high in sugar, alcohol, and processed foods, can weaken the immune system and lead to cold sore outbreaks.

Hormonal Changes

Any change in hormones can trigger a cold sore outbreak. Pregnancy is the most notable of these hormonal shifts, but many women also experience cold sore outbreaks just before or during their menstrual cycle.

You can track your menstrual cycles to know when you'll be most susceptible to cold sores. That way in the future, you can bump up your self-care regimen during those times.

Viral Illnesses

When your immune system is fighting off another type of virus such as a cold or the flu, it becomes less able to suppress HSV-1. Guard against these viruses by washing your hands frequently and giving your body plenty of rest.

Stress and Fatigue

Similar to viral illnesses, stress and fatigue take a toll on the immune system and make the body less capable of suppressing HSV-1. Finding ways to deal with stress and making sure you get enough sleep can help prevent cold sore outbreaks.

Because of the combination of excessive alcohol intake and missed sleep, people often notice a pattern of cold sore outbreaks related to partying.

Dental Work

Pressure on the lips from extended dental work can cause some people to experience a cold sore flare-up. You can apply a cold compress to your lips after your dental visit to help soothe the area and decrease inflammation.

Also, be sure to reschedule your dental appointment if you have an active cold sore.

Exposure to Harsh Wind, Cold, or Sun

Dried, cracked lips are more susceptible to developing cold sores. Make an effort to keep your lips moist and drink plenty of water. You can use a scarf or mask to cover your mouth if you know you'll be exposed to harsh sun, wind, or bitter cold for an extended period of time.


What's the Cure for Cold Sores?

Unfortunately, there's no cure for cold sores or HSV-1. Once you contract the virus, the best way to prevent future outbreaks is to maintain a consistently high level of basic self care.

Manage your daily stress, keep yourself well hydrated and restrict your alcohol and sugar intake to moderate levels. It is good to give your body plenty of nourishment through lean protein, fruits, and vegetables

Create a sleep-friendly environment at night and take nutritional supplements like zinc, omega-3 fatty acids, probiotics, and lysine to boost your immune system.

Try phototherapy, like that provided by the Luminance RED Lip Sore Treatment Device, at the first sign of a cold sore to decrease pain, speed healing, and decrease the frequency of cold sore outbreaks.

There may not be a cure for cold sores, but by arming yourself with knowledge about what causes cold sores, you can take proactive steps to effectively manage them.

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