Fever Blisters & Ulcers:
Fever blisters are caused by the herpes simplex virus type 1 (HSV-1), a virus that passes from person-to-person by direct contact with infected skin or secretions, including saliva. The sores usually appear as clusters of tiny blisters on the lip. HSV-1 can cause similar, but smaller, blisters that rapidly become ulcers inside the mouth on the gums and palate (roof of the mouth).
The first time HSV-1 invades the skin, it causes a primary infection, which usually occurs in childhood or adolescence. It may cause a fever, sore mouth and sore throat. The primary infection often is similar to other viral or bacterial throat infections, and often is not diagnosed as an HSV-1 infection.
After this primary infection subsides, the virus remains dormant (inactive) indefinitely in nerve roots near the affected skin area. In some people, the virus becomes active again from time to time and causes new active sores on the skin, usually on the lip. These sores have become known as cold sores or fever blisters because the virus can be reactivated by a cold or fever. The virus also can be triggered to become active again by other factors, including stress, trauma to the lips, exposure to the sun's ultraviolet rays, menstruation and suppression of the immune system.
In addition to causing infections around the mouth, HSV-1 can be transferred to the eyes, the skin of the fingers, the genital area and elsewhere. Most genital herpes infections are attributed to herpes simplex type 2 (HSV-2), but HSV-1 can cause genital infections in some people. HSV-1 can cause unusually severe illness in people debilitated by other health problems (malnutrition, cancer or weakened immune systems, including AIDS) or those receiving cancer chemotherapy, corticosteroids or drugs to prevent the rejection of organ transplants.
HSV-1 infections are very common in the United States, and most of us are infected by the time we reach adulthood. Even if we do not remember having a primary HSV-1 infection during childhood, the fact that we occasionally have a cold sore or fever blister indicates that HSV-1 is present.
Causes of Mouth Ulcers or Sores
- Canker Sores. The main cause of 1 or 2 mouth ulcers after age 5.
- Hand-Foot-Mouth Disease. The most common cause of multiple ulcers in the mouth. These ulcers are mainly on the tongue and sides of the mouth. Most children also have small deep blisters on the palms and soles. Due to the Coxsackie virus. It is common between ages 1 to 5 years.
- Herpes Simplex Virus (Cold sore virus). The first infection can be severe. It can cause 10 or more ulcers on the gums, tongue and lips. Key findings are additional ulcers on the outer lips or skin around the mouth. Also, fever and difficulty swallowing. Usually occurs age 1 to 3. It usually follows contact with an adult who has active cold sores (fever blisters). Often they have kissed the child.
- Cold Sores (Fever Blisters). Sores are only found outside the mouth on the outer lip. They recur 2 or 3 times a year in the same place. There are no ulcers inside the mouth. Adult cold sores are the cause of Herpes Simplex infections in young children. Occurs in 20% of teens and adults.
- Mouth Injury. Common mouth injuries are biting the tongue or inside of the cheek. Others can be caused by a toothbrush. The lining of the mouth always looks white when it heals. So forgotten injuries can look like a canker sore.
- Mouth Burns. Hot foods (such as pizza) can cause mouth sores. They also turn white as they heal.