Damage to the cells that make up the moist tissue lining your mouth and digestive tract is a common side effect of chemotherapy treatment, including methotrexate and 5-fluorouracil. Mucositis causes painful swelling of the mouth and tongue and can lead to bleeding, pain, and mouth ulcers. The condition can make it difficult to eat.
You're more likely to develop mucositis if you drink alcohol, use tobacco, don't take care of your teeth and gums, are dehydrated, or have diabetes, HIV, or kidney disease.