Cold sores are common among the US population and across the globe. According to health reports, 90% of US adults have been exposed to the virus responsible for cold sores (herpes simplex virus type 1) by the time they reach the age of 50.¹ Globally, the prevalence of oral herpes is about 67% among adults aged below 50 years.²
While cold sores mainly occur around the lips, they can also develop inside the mouth and at the back of the throat. They can also appear around the eyes, nose, and cheeks.
People with recurrent herpes infections can have more than one outbreak in a year. Usually, the cold sores clear up on their own after seven to ten days, but seeking treatment helps ease the pain.
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Cold sores are small fluid-filled blisters that occur mainly along the border of the lips but may also develop on the nose, cheeks, eyes, and back of the throat. In rare cases, they can also develop cold sores on the fingers due to HSV-1 infection. Known as herpetic whitlow, the finger infection can also be caused by HSV-2 after contact with infected genitals.
Cold sores are contagious and can spread through contact, such as kissing. Once the blisters break, they leave a scab which clears without leaving a scar in 10–15 days.
The sores are usually painful, especially during the first outbreak, so treatment is recommended to help relieve the pain and quicken the healing. Also, if the infection is on your eyes, it can lead to permanent vision loss if left untreated.
Cold sores are caused by the virus known as herpes simplex virus type 1 (HSV-1), although exposure to the virus does not automatically lead to the outbreak of cold sores. It might take up to 20 days before the blisters break out.
Once the sores clear, the virus lies inactive within the nerve cells. You can have a recurrence triggered by factors such as:
Changes to the immune system, like an illness
The recurrence is usually less severe than the first outbreak.
Generally, you can get HSV from contact with infected people or things. This can be through kissing or sharing eating utensils, towels, and razors.
While HSV-1 is the most common cause, HSV-2 (responsible for genital herpes) can also cause cold sores through oral sex. The virus is most contagious during the active stage, but you can also get infected even if the person does not have blisters.
Yes. While cold sores mainly occur outside the mouth, they can also develop at the back of the throat. The condition is usually referred to as herpes esophagitis and may cause symptoms like:
Difficulty while swallowing
Cold sores start with tingling and itching before the blisters form. The signs and symptoms may vary depending on whether it's the first outbreak or a recurrence.
Burning and painful gums
Swollen lymph nodes
Outbreak of cold sores
When cold sores develop inside the mouth, such as at the back of the throat, you may confuse them with canker sores (mouth ulcers) since both conditions cause similar pain and discomfort. However, canker sores are quite different.
Unlike cold sores, canker sores cannot be spread from one person to another and don't develop outside the mouth. Instead, they're flat lesions (ulcers) that form on the inside cheeks and lips, under the tongue, throat, and on the tonsils. Canker sores are brought upon by stress, acidic foods, or minor trauma to the inside of the mouth (e.g., if you bite the skin).
If you look into your throat, you should be able to tell if it's a cold sore or a canker sore. A cold sore is a cluster of fluid-filled blisters, while a canker sore is a single flat ulcer.
Strep is a bacterial infection, otherwise known as group A Streptococcus. It might present similar symptoms as cold sores in the throat, such as a sore throat, fever, or difficulty swallowing. However, instead of the fluid-filled sores, it forms white spots on the tonsils.
If you consult with your doctor, they will consider your symptoms, do a physical exam, then carry out a strep test.
Cold sores do not suddenly appear. They develop in five stages:
Tingling: At first, you will experience a tingling, itchy feeling around the mouth.
Blistering: After 24–48 hours, fluid-filled blisters form on the skin surface where you experience the tingling.
Weeping: A few days later, the blisters break open.
Crusting: The blisters then dry up and crust over.
Healing: Finally, the scab flakes away without scarring.
Cold sores are diagnosed by examining the blisters. However, if the diagnosis is unclear, the doctor may swab the blister and examine the sample for HSV. This is achieved via a polymerase chain reaction test, which checks for the genetic material of the virus.
Since the sores are caused by a viral infection, they cannot be cured. However, several treatment options are available to manage the infection and relieve the symptoms.
Treatment can help to prevent recurrence for some people and ensures any recurring symptoms are less severe than the first outbreak.
Treatment options include:
Antiviral topical ointments and creams
Antiviral oral medications (pills)
Intravenous medications (injections into the bloodstream)
Antiviral treatment options tend to be most effective if you take them immediately after an outbreak.
You can try some home remedies to relieve the symptoms, such as:
Cold, damp compresses
Applying lip balm containing lemon extract or aloe vera
Once you’ve had an outbreak, you can prevent recurrence by controlling potential triggers. For instance, getting enough rest and minimizing sun exposure by using products with sunscreen. Some research suggests that lysine supplements could help to reduce outbreaks, but more research is needed.³
You can also curb the spread of the virus by avoiding the following activities, especially when active blisters are present (transmission can still occur without active blisters, but the rates are lower):
Sharing eating utensils, towels, razors, and lip balm
Lastly, if you have a cold sore, avoid touching the blisters and wash your hands after applying the medication.
While cold sores mainly occur outside the mouth, they can also develop at the back of the throat. While there isn’t a cure for cold sores since they are viral infections, treatment helps relieve the symptoms and weakens the severity of a recurrence.
You can also prevent cold sores by refraining from kissing, having oral sex, and sharing eating utensils and other personal items, such as towels, with an infected person.
Yes. A sore throat is a common symptom of cold sores at the back of the throat.
Yes. While cold sores are not caused by the flu virus, they can give you flu-like symptoms.
A cold sore can make you feel ill, especially during the first outbreak, due to symptoms such as headache, nausea, and fatigue. However, it's caused by a viral infection whose symptoms usually go away without treatment.
Oral herpes | Johns Hopkins Medicine
Herpes simplex virus | World Health Organization