How the Symptoms and Appearance Differ Between Cold Sores and Canker Sores

Canker sores, also known as aphthous ulcers, are mouth ulcers that look like a shallow disc and are often oval or round. These lesions can be whitish, grayish, or yellowish, and they are usually less than 1 millimeter in diameter.

A canker sore can develop as a single sore, or you may have clusters of tiny sores. These sores can be painful, making it difficult to eat, talk, and brush your teeth. But the pain usually improves after a couple of days.

A cold sore, also known as a fever blister, starts as a tiny fluid-filled blister or a cluster of them. You may notice itching or tingling one to two days before the blisters appear. These sores can cause skin redness and pain, and they eventually rupture and ooze before a scab forms.

During a first cold sore outbreak, additional symptoms may include a fever, swollen glands, sore throat, headache, and muscle aches.

Location Matters When Figuring Out if It’s a Cold Sore or a Canker Sore

The location of these lesions is another way to determine a cold sore from a canker sore. Canker sores develop on the mucous membranes inside the mouth. Therefore, you’re more likely to find these sores on the inside of the cheeks and lips, gums, soft palate, or tongue.

Cold sores, on the other hand, don’t usually appear inside the mouth, although this is possible when you are first exposed to the virus that causes them.

Instead, cold sores often develop on or around the lips.

They can also form on other parts of the body, such as the cheeks and around the nose. The virus sometimes infects people’s eyes.

The Cause of a Cold Sore Isn’t the Same as the Cause of a Canker Sore

Cold sores are most commonly caused by the herpes simplex virus type 1 (HSV-1). This is a common virus — more than 50 percent of Americans ages 14 to 49 carry it.

Many people get the virus as a child after being kissed by someone who is infected.

Some infected people never develop a cold sore because the virus can lie dormant in the body for years.

Certain factors can reawaken the virus and spark a cold sore:

Exposure to strong sunlight
Stress
Tiredness
A fever or infections
Hormonal changes
Facial procedures or laser treatment

HSV-1 and HSV type 2 (HSV-2) are viruses that can cause cold sores, as well as genital herpes. You can get HSV-2 cold sores if you engage in oral sex with someone who has genital herpes, but this isn’t the only way to spread these types of cold sores. A person with HSV-2 cold sores can infect another person through kissing, too.

Likewise, HSV-2 can also be transmitted from a mother’s genital tract to her newborn infant, says Allison Arthur, MD, a board-certified dermatologist at the Sand Lake Dermatology Center in Orlando, Florida.

Canker sores, on the other hand, aren’t caused by the herpes virus. The exact cause of canker sores is unknown. But it’s believed that certain factors can increase your risk. Some people get a canker sore after eating citrus fruits or acidic foods, whereas others develop sores because of a nutritional deficiency (in, for example, vitamin B12, folic acid, or iron).

Certain medications, such as nonsteroidal anti-inflammatory drugs like ibuprofen, can also cause canker sores.

Other factors that can trigger a canker sore include smoking, stress, and an injury inside the mouth.

Some autoimmune diseases and a weakened immune system are associated with canker sores as well.

How Cold Sores Are Spread Is Different From Canker Sore Transmission

Another difference is how these lesions spread. Cold sores are contagious. Not only do they spread from person to person through kissing, but also through sharing eating utensils, drinks, and personal items.

It’s important that you don’t kiss or share food or drinks with someone who has an active cold sore. You should also wash your hands after touching a cold sore. This prevents spreading a cold sore to others, as well as spreading the virus to other parts of your body.

Cold sores are most contagious when blisters rupture. But you can still pass the virus to others until the sore is completely healed.

A canker sore, on the other hand, isn’t contagious and doesn’t spread from person to person.

A Final Word on How Cold Sores Are Different From Canker Sores

Even though these sores differ, they do share some similarities. It usually takes between one and three weeks for cold sores and canker sores to heal, and they often go away on their own without treatment.

Some people also deal with recurrent cold sores and canker sores. For a recurrent cold sore, ask your doctor about suppression therapy with a daily antiviral to reduce the frequency of outbreaks. You should also see a doctor for repeated canker sores. This can be a sign of an autoimmune disease or a vitamin deficiency.

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