Cold sores: How they’re triggered and what you can do about them

Before a big work presentation, before a first date, before picture day: Cold sores can appear at the worst times. When you need them gone fast – whether you have your first-ever cold sore or get them all the time – you need to understand how they happen.

Cold sores are extremely common: According to the American Academy of Dermatology, more than half of all Americans between the ages of 14 and 49 have the herpes simplex virus, or the virus that causes cold sores. While cold sores are nothing to be ashamed of, that doesn’t stop them from being embarrassing, uncomfortable and downright annoying.

Below, we’ll talk about what causes cold sores, how they’re spread, the best at-home cold sore treatments and when to see a doctor.

A cold sore is a small, recurring cluster of blisters

A cold sore, also known as a fever blister, is a cluster of tiny, fluid-filled blisters that appears on or around your lips or chin. In rare cases, cold sores can also form on your nose.

Cold sores are caused by the herpes simplex virus, or HSV. The virus lives in the nerve cells in and around your lips. When you get a cold sore, it’s called an outbreak or flare-up. Most people have between 2-3 cold sore outbreaks in a year, but about 5-10% of people with HSV get around five cold sore outbreaks in a year.

Symptoms of cold sores follow a rhythm

A few days before a cold sore appears, you’ll experience a tingling, itching and burning sensation in the area. This is called the prodromal stage. If this is your first outbreak (known as a primary outbreak) you may also experience mild flu-like symptoms, such as swollen lymph nodes, a sore throat or headache. The primary outbreak typically lasts longer than any subsequent outbreak, sometimes as long as 2-3 weeks.

A few days after the prodromal stage, a cluster of tiny, painful, fluid-filled blisters will form on the lips or the skin around them, and sometimes the chin and nose.

HSV: The virus that causes cold sores

Cold sores are caused by the herpes simplex virus (HSV), or more specifically, a strain of HSV known as HSV-1. It’s also called oral herpes, which is different than genital herpes.

There is currently no cure for HSV. Once you have the virus, it stays in your body for life and lies dormant in your nerve cells. It resurfaces from time to time, resulting in cold sore outbreaks.

People with HSV have varying experiences. Some people never get a cold sore, others get one cold sore and then never get another, and some have frequent cold sores that become more sporadic as they age. It depends on your unique immune system and lifestyle.

Cold sore outbreaks are caused by triggers

A cold sore “trigger” is anything that causes the herpes simplex virus to flare up inside your body. Everyone’s triggers are different, and identifying yours can help prevent future cold sore outbreaks. When you feel a cold sore coming on, it may be helpful to go through the events of your last few days and see if anything sticks out. Cold sore outbreaks can be triggered by:

Environmental conditions

Exposure to extreme weather, whether it’s very cold or very hot outside, can trigger cold sores. In addition, sunlight and wind can lead to sunburn and windburn, both of which are common cold sore triggers.

A weakened immune system

When your immune system is trying to fight off other illnesses, like the common cold or the yearly flu, it doesn’t have as many resources to combat HSV. The virus can then resurge, leading to a cold sore outbreak. Many people get a cold sore every time they get sick, hence why it’s called a “cold” sore or sometimes a fever blister.

Lifestyle factors

Taking care of your mind and body can help you stay well in general, but it’s especially important if you’re struggling with cold sores. Stress is a common trigger for many people with HSV, so get regular exercise and practice other relaxation techniques to help manage your stress levels.

Diet can also be a cold sore culprit. Some studies suggest that the amino acid arginine – found in chocolate, wheat, nuts and seeds (especially pumpkin seeds), squash and oats – causes cold sores. Coffee and red wine may also be triggers. To prevent cold sores, avoid these foods, drink caffeine and alcohol in moderation, stay hydrated, don’t smoke and get plenty of sleep.

Fluctuating hormone levels

People with periods may find that their cold sore outbreaks follow their menstrual cycle. You can also get cold sores more frequently during pregnancy or menopause.

Cuts or other skin irritation

Trauma to your lips and the skin around your mouth – cuts and bruises, even razor burn – can cause an HSV flare-up and subsequent cold sore. This is why it’s important to treat any facial injury right away by disinfecting and icing the area.

In a person with eczema, a cold sore can lead to a serious, widespread skin infection called eczema herpeticum. If you have eczema and oral herpes, talk to your doctor about managing both conditions.

How are cold sores spread?

The virus that causes cold sores is very contagious, especially during an outbreak. Transmission tends to occur between intimate partners through kissing, but the virus can also spread between family members through shared household items or kisses on the cheek.

Any activity that brings an active cold sore into direct contact with someone else’s mucosal skin (the skin of the genitals, the lips, and the inside of the mouth and nose) can transmit the herpes simplex virus.

To avoid spreading the herpes simplex virus, don’t engage in intimate contact during a cold sore outbreak. It’s important to be honest and upfront with sexual partners about your status.

The herpes simplex virus doesn’t survive long once it’s outside the body, so it can’t be spread through coughing or sneezing, but it can linger on surfaces. During a cold sore outbreak, you should always wash your hands with soap and water after touching the area around your mouth, and avoid sharing utensils, cups, straws, lip balm, lipstick and other personal-use items that touch your mouth.

When a cold sore is most contagious

Cold sores are contagious from when they first appear until they go away, but they can be especially contagious during certain stages of an outbreak. Each time you get a cold sore, the outbreak should follow the same five stages:

• An itching, tingling or burning sensation starts on and around your lip (known as the prodromal stage)
• One blister or a tight cluster of blisters form
• A few days later, the blisters burst and drain fluid (this is when they are most contagious)
• The blisters scab over
• The scab heals and falls off, leaving clear skin behind

This progression occurs over the course of 7-10 days. Cold sores will remain contagious until the outbreak has completely resolved, but be extra careful once the blisters burst and drain their fluid as this is when HSV is most contagious. When skin has completely cleared, it’s safe to have skin-to-skin contact with others again.

Cold sore outbreaks often decrease in severity and frequency over time. Your cold sores are worst when you first contract the virus, but lessen with each subsequent outbreak.

While cold sores will typically heal on their own after 7-10 days, you can help them heal faster and with less pain by using treatments at home

At-home treatments

As soon as you feel the tingling, itching or burning that signals an oncoming cold sore, begin treatment. Addressing it early will shorten the severity and duration of the cold sore.

Here’s what you can do:

• Use cold compresses on the area
• Eat mostly cold, soft foods, and avoid salty, spicy or acidic foods
• Suck on ice or popsicles
• Apply over-the-counter antiviral cold sore cream (dab it on, don’t rub it in)
• Protect the cold sore area with a layer of petroleum jelly, or use anesthetic ointments like lidocaine or benzocaine
• Wear a lip balm with sunscreen to avoid sunburn
• Take over-the-counter pain relievers like ibuprofen or acetaminophen
• To avoid infection or further irritation, wait until your cold sore has scabbed over before putting makeup on it

Anytime you touch a cold sore, wash your hands thoroughly before and after. When using ointments or creams on a cold sore, you can use a cotton swab as your application tool.

When to see a doctor about cold sores

Cold sores usually heal on their own in 7-10 days, and it’s normal to have 3-4 outbreaks or flare-ups in a year. If you do get a flare-up, your primary care doctor can prescribe an antiviral medication that can lessen the severity and duration of your cold sore symptoms. These medications are most effective when they are taken within 72 hours of when cold sore symptoms begin.

You should see a doctor or clinician if cold sores become more frequent – with one or more outbreak in a month or 6-8 within a year – or if you have HSV and a compromised immune system. Also, check in with your doctor if you get a cold sore that lasts longer than three weeks, is especially large and painful, or begins to spread beyond the original outbreak area.

If you have an active cold sore and would like a definitive diagnosis, your primary care doctor or clinician should be able to determine whether it’s oral herpes through a physical exam alone. Otherwise, they might swab the sore for testing or check your blood for HSV antibodies.