Cold Sores: Causes, Symptoms & Treatment

A lot of different things can cause bumps and lumps on or around your mouth.

So when a new mouth sore pops up, you may not be certain if it’s a cold sore, canker sore, or something possibly more serious.

To add to the confusion, cold sores are also called fever blisters, though they are not related at all to having either a cold or a fever.

The good news is, while common and annoying, cold sores typically aren’t cause for concern.

And once you have one, you can usually tell when another one is getting ready to appear—and use over-the-counter (OTC) or home remedies to head it off or at least help it heal faster.

In this article, I’ll explain everything you need to know about cold sores, including the causes, symptoms, risk factors, diagnosis, treatment, complications, and prevention tips. 

Causes 

Most cold sores are caused by type 1 herpes simplex virus (HSV).

This highly contagious virus spreads through skin contact (such as kissing or oral sex) or by sharing items that touch your mouth (like cups and razors) or are spread from parents to children. 

Though HSV-1 can also cause genital herpes, more often, herpes simplex type 2 causes genital herpes. HSV-2 can also cause oral herpes, though this is less common. 

With either type of herpes virus, after the initial outbreak heals, the virus goes dormant but never leaves the body. New outbreaks can happen if the virus reactivates, although sometimes reactivation never occurs.

Symptoms

Some people have no symptoms before a cold sore outbreak. Others only have symptoms the first time they are exposed to type 1 herpes simplex virus.

Symptoms of a first infection may include:

• Lesions or sores around the lips (or less commonly on the tongue, cheeks, chin, or around the nose)
• Sore throat
• Swollen lymph nodes
• Headache
• Nausea

Around 30% of people who have type 1 herpes simplex virus have recurring outbreaks of cold sores that tend to reappear in the same places each time.

With a reinfection, a tingling or burning sensation is the only symptom, if any, that typically precedes the development of a cold sore.

Stages of symptoms

Recurring cold sores develop in predictable stages and last for 1-2 weeks:

• Stage 1: A tingling, itching, burning, or numbing sensation may occur in the spot where outbreaks usually occur. This may happen about 1-2 days before the sore appears.
• Stage 2: One or more painful cold sores appear around the mouth.
• Stage 3: After several days, the sores break open. This is when someone is most contagious.
• Stage 4: A yellow or brown crust covers the sores.
• Stage 5: The crust comes off and a scab forms. The scab eventually flakes off, though more scabs may continue to form until the sore goes away.

Risk Factors

More than 50% of American adults have been exposed to HSV-1 and are at risk of developing cold sores. Factors that increase the likelihood of cold sore outbreaks include: 

• A compromised immune system
• HIV/AIDS
• Chemotherapy treatment for cancer
• Anti-rejection drugs for organ transplants
• Eczema

In addition to these conditions and treatments, some other health and lifestyle factors often trigger cold sore outbreaks. This includes:

• Sunshine exposure or sunburn
• Stress
• Fever
• Colds or other viral illnesses
• Fatigue
• Eating foods high in the amino acid arginine (such as peanuts, grains, legumes, and some meats)
• Hormonal changes associated with the menstrual cycle

Diagnosis 

If you have had cold sores before, you’re likely familiar with the signs of recurrence. If you have never had a cold sore, a doctor or health care professional can confirm a diagnosis by examining the sores.

You do not always need to see a healthcare provider for cold sores, even if it is your first time having them.

However, you should get medical care under the following circumstances:

• Your symptoms are severe
• You have underlying conditions that could make cold sores worse (such as HIV/AIDS, eczema, or cancer)
• Your cold sores do not begin to heal after two weeks
• You frequently get cold sores

Treatment

Cold sore outbreaks typically heal on their own in 1-2 weeks without treatment.

Still, they can be uncomfortable and unsightly, so you may wish to try one of the following treatments or remedies to speed the healing process. The best time to treat a cold sore is at the first sign of symptoms.

Antiviral medications

Oral antiviral medications may prevent recurring outbreaks and speed the healing of cold sores, but they do not remove the virus from the body.

Common prescription antiviral medications used to treat cold sores include:

• Acyclovir (Sitavig, Zovirax)
• Famciclovir (Famvir)
• Valacyclovir (Valtrex)

Antiviral creams

Topical antiviral creams may help shorten the duration of a cold sore outbreak by about one day. Some are available over the counter (OTC), while others require a prescription.

OTC options include:

• Docosanol 10% (Abreva)
• Benzyl alcohol (Zilactin-L)
• Dimethicone with sunscreen (Herpecin-L)

Prescription creams for cold sores include:

• Penciclovir cream (Denavir)
• Acyclovir cream (Zovirax)
• Benzocaine gel (Zilactin) to numb the area

Each type of cream may have different instructions, so read the label carefully.

Home remedies

Some people swear by home remedies for cold sores, but ask your doctor if any are safe before you try them.

There’s limited scientific evidence suggesting that treatments such as those below work: 

• Petroleum jelly
• Lavender or tea tree essential oil
• Lysine (oral, topical cream, or lip balm)
• Rhubarb and sage cream
• Propolis ointment

Also, since stress can be a trigger for cold sore outbreaks, finding ways to support your mental health may help decrease the chance of recurring outbreaks.

Pain relief 

Cold sores can also cause mild to moderate pain.

Some OTC pain-relief gels, such as benzocaine (Anbesol, Orajel), may help to alleviate discomfort but will not speed healing. Ibuprofen (Advil, Motrin) and acetaminophen (Tylenol) also work for pain relief when you have a cold sore.

Complications

It is rare for oral herpes simplex to cause complications. When it happens, it’s most often in people with weakened or compromised immune systems.

Complications of cold sores include:

• Herpetic whitlow: This infection on the fingers enters the body through a cut on the skin, leading to swelling, red skin, and painful blisters. 

• Herpetic keratoconjunctivitis: This eye infection affects the cornea (the dome covering the front of the eye) and can cause blurry vision, eye pain, and, if not properly treated, blindness.

• Encephalitis: This infection spreads to the brain and can cause life-threatening swelling.

Prevention

If you have been exposed to the herpes simplex virus, you cannot always prevent cold sores.

However, by being familiar with the early signs, you can intervene and prevent outbreaks:

• At the first sign of tingling, use an OTC or prescription antiviral topical cream.
• Use sunscreen if sunlight is a trigger.
• Keep the lips moisturized.
• Manage stress in a healthy way.

If you have cold sores, you can avoid spreading them to others by:

• Not kissing or having close contact with anyone while you have an active outbreak.
• Washing your hands after touching your face.
• Avoiding sharing cups, towels, lip balms, utensils, and any other personal items.

How K Health Can Help

Did you know you can get affordable primary care with the K Health app? Download K Health to check your symptoms, explore conditions and treatments, and if needed text with a provider in minutes. K Health’s AI-powered app is based on 20 years of clinical data.