Key Points
- Cold sores (also known as fever blisters) present with fluid-filled bumps, while canker sores (also known as aphthous ulcers) appear as flat yellow ulcers with a red border.
- Cold sores usually appear on the outside of the lips and around the mouth, while canker sores appear inside the mouth.
- Cold sores are very contagious, while canker sores are not contagious.
- Cold sores are treated with antiviral medications, while canker sores may be treated with steroids, although both these sores may also resolve on their own.
Sores on the lips can be due to different reasons. Cold sores and canker sores are the common ones. The causes behind them and their treatment are entirely different, so it’s important to identify them.
Additional names
Both cold sores and canker sores are also known by other names, so it’s important to know the terminology to avoid confusion.
Cold sores are also known as fever blisters, oral herpes, and herpes simplex labialis, while canker sores are known as aphthous ulcers.
Pictures
Below, you will find pictures comparing canker sores and cold sores, which can provide an overview of their appearance.
Causes
Cold sores
Cold sores occur due to an infection by the herpes simplex virus, usually type 1. Once a person is infected, the virus stays inside the body for life. Under certain conditions, the virus can reactivate and lead to an outbreak.
The precipitating factors are:
- Immunosuppression
- Fatigue
- Illnesses like colds and fever
- Excessive sun exposure
- Allergies
- Stress
- Menstruation
- Dental or cosmetic treatments
Canker sores
It is not clear what really causes canker sores, but they are associated with several factors that can trigger an outbreak. These include:
- Any injury inside the mouth
- Stress
- Food sensitivities
- Certain oral care products
- Hormonal changes
- Nutritional deficiencies of vitamin B12, folate, zinc, or iron.
They may also be associated with inflammatory bowel disease, reactive arthritis, Behcet’s disease, celiac disease, or HIV.
Symptoms
Cold sores
Cold sores usually lead to painful fluid-filled blisters on the outside of the lips. These bumps can also appear around the mouth, on the cheeks, nose, or near the eyes.
The symptoms can vary depending on whether it is the primary/first infection or a recurrent episode. The first infection leads to more severe symptoms, and cold sores may be accompanied by fever, swollen or enlarged lymph nodes, a sore throat, or fatigue.
Additionally, the primary infection can lead to sores inside the mouth – on the gums, inside the cheeks, or lips, while recurrent episodes more often lead to sores on the outside of the lips.
The cold sores go through several phases. These include:
- A person may feel tingling, itching, or burning in the lip area.
- In a few hours, fluid-filled blisters may appear.
- These can burst and ooze and eventually scab.
- The scab falls off.
Cold sores are very contagious, and one should not touch other parts of the body after touching a cold sore. This will prevent the transfer of the virus. A person stays contagious until the skin lesions heal completely.
Canker sore
Before the appearance of a canker sore, a person may feel a tingling or burning sensation in an area. The painful sore appears as a yellow or white shallow ulcer with a red border. These appear on the mucosal surfaces – inside the lips or cheeks, on the tongue, or on the roof of the mouth.
They can be of different sizes, based on which they can be categorized as follows:
- Minor canker sores (the most common type) are usually less than 1 cm and round or oval in shape.
- Major canker sores are larger (2-4 cm) with irregular borders and can take longer to heal. They can be very painful.
- Herpetiform canker sores (no association with the herpes virus) are less common and are 1-2 mm in size. These appear in clusters of 10-100s.
Unlike cold sores, canker sores are not contagious.
Diagnosis
Both cold sores and canker sores can be diagnosed by clinical examination. The location and appearance can help in differentiation.
Fever blister: It presents with fluid-filled blisters on the outside of the lips. In some cases, your doctor may take a swab to test the fluid for the virus.
Canker sore: It presents as a yellow ulcer with a red border, usually located inside the lips. In some cases, your doctor may conduct additional testing to rule out nutritional deficiencies or other causes.
Treatment
Cold sores
- Mild cases of cold sores may not require any treatment and may heal on their own. In severe and persistent cases, medication may be prescribed.
- A cold compress can help in easing some discomfort.
- Over-the-counter balms and gels may contain a numbing agent like benzocaine (e.g., Carmex) which can provide some relief from discomfort and pain.
- Moisturizers can prevent dryness, and lip sunscreen can protect the area from UV rays.
- Abreva cream is available over the counter; it contains an antiviral – docosanol. This can help in faster healing of cold sores.
- In some cases, oral or topical antivirals may be prescribed, like acyclovir.
- One should avoid acidic, spicy, and salty foods to avoid irritating the affected areas.
- One should see a doctor if the sores do not heal, there are sores near the eyes, there is eye irritation, or any other systemic symptoms like headache, confusion, or dizziness.
Canker sores
- Just like cold sores, mild cases of canker sores do not require treatment, and the sores clear in a week or two. Large and recurrent sores may require treatment.
- Over-the-counter mouth rinse with chlorhexidine gluconate or hydrogen peroxide may be helpful.
- In some cases, mouth rinses with steroids may be prescribed.
- Steroid ointments may also be used.
- In more resistant cases, the sore may be cauterized. To cauterize (burn) the sore, either a topical like silver nitrate or an instrument may be used.
- If there is any nutritional deficiency, vitamin supplements may be recommended.
- One should avoid hot, spicy, salty, and acidic foods to prevent further irritation of the area.
- One should see a doctor if the sores do not heal or are large and interfere with drinking and eating.
Prevention
Both cold sores and canker sores can occur due to certain precipitating factors. The following measures may decrease the outbreaks.
Measures to prevent cold sores
- Always protect your lips from the sun by using a broad-spectrum sunscreen.
- Get good rest daily to avoid fatigue.
- Practice good hand hygiene to avoid getting sick.
- De-stress through meditation, walking, or listening to music.
- Do not share personal items with anyone who has a cold sore.
Measures to prevent canker sores
- Eat a healthy diet to avoid nutritional deficiencies.
- Avoid foods to which you are sensitive.
- Reduce your stress.
- Avoid very spicy and hot foods.
- Avoid injuring your mouth while brushing or flossing.
Summary
Cold sores and canker sores are some of the common reasons for lip sores. Cold sores usually appear outside the lips and are characterized as fluid-filled blisters, while canker sores appear inside the lips or mouth and look like yellow ulcers with a red border.
Cold sores are due to a viral infection, while the exact cause of canker sores is not known. Cold sores are very contagious and can spread from one person to another through close contact, but canker sores are not contagious.
Mild cases of both usually do not require treatment; however, persistent or severe cases may need medical attention and prescription medication.
Read more:
- Cold sores: Causes, Treatment, Fever blisters vs cold sores
- Cold sores pictures and symptoms
- Cold sores stages, with pictures
- Does Carmex Help Cold Sores?
References
- Plewa MC, Chatterjee K. Aphthous Stomatitis. [Updated 2022 Aug 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan.
- Saleh D, Yarrarapu SNS, Sharma S. Herpes Simplex Type 1. [Updated 2022 Aug 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan.
Disclaimer: This blog post is for information purposes only and does not replace medical advice.