Oral mucositis and gastrointestinal mucositis can sometimes lead to other problems.

Pain when swallowing

Most people with oral mucositis will experience pain when swallowing. Until your symptoms subside, you may find it easier to switch to a diet containing softer foods, such as mashed potatoes or scrambled eggs.

Feeding tubes may be required in cases severe enough to place you at risk of becoming malnourished and dehydrated. You'll probably be given a nasogastric tube, which is a tube that passes down your nose and into your stomach.

The tube can usually be removed after your ulcers heal and your ability to swallow has returned.

Infections

Mouth ulcers can sometimes become infected. This makes them difficult to heal and antibiotics may be needed to treat them.

If you also have a weak immune system and a mouth ulcer becomes infected, there's a risk that the infection will spread in your body. This is known as blood poisoning, or sepsis, and requires urgent assessment and treatment in hospital with antibiotics.

In the most serious cases of blood poisoning, multiple organ damage can cause a large drop in blood pressure. This is known as septic shock and requires immediate treatment in an intensive care unit (ICU). This is so the functions of the body can be supported while the infection is treated using antibiotics or antiviral medication.

Read more about blood poisoning and septic shock.