Methotrexate is one of the most commonly prescribed — and most effective — disease-modifying antirheumatic drugs for treating rheumatoid arthritis (RA). Occasionally, side effects can occur from taking methotrexate for RA. For example, mouth sores can develop.

As many as one-third of people with RA taking methotrexate end up with mouth sores or ulcers, according to the Arthritis Foundation. Mouth sores of any kind can be unpleasant, especially if they’re a side effect of your RA medication.

Ask your rheumatologist or a health care professional for medical advice if you develop mouth sores while taking methotrexate. Your doctor can recommend several options to address mouth sores, depending on their severity, without jeopardizing your RA treatment. People on myRAteam also offer suggestions for managing mouth sores caused by methotrexate.

Members of myRAteam on Mouth Sores From Methotrexate

Some myRAteam members have discussed developing mouth sores when taking methotrexate. “Has anyone here had mouth sores from methotrexate?” asked one member. “I’ve been getting little ones. I thought they were canker sores at first, but they aren’t. They started a couple of weeks ago, and when one heals, another shows up.”

Another member had a similar question: “I’ve been taking RA medication for five months, and I have noticed almost constant canker sores and cold sores for the past four months. Has anyone else had this happen?”

“Unfortunately, with the [immune system] suppression from medication,” wrote a member, “it can cause blisters and sores. I used to get them all around my mouth.”

Some members have even found that soreness and discomfort affect the entire mouth, such as one member who shared, “I was put on methotrexate last month, and my whole mouth is sore.”

How Can Methotrexate Cause Mouth Sores?

Methotrexate is an immunosuppressant — it prevents the immune system from attacking healthy cells and causing RA symptoms. The drug is among a group of RA treatments that help manage symptoms such as joint pain, stiffness, and swelling and slow the progression of disease.

Experts believe that methotrexate treats RA by preventing the production of inflammation-causing chemicals and blocking cells’ access to folate, a B vitamin. The vitamin’s synthetic form is called folic acid.

Although methotrexate successfully helps reduce inflammation, decreasing the amount of folate in the body can harm cells in the digestive (gastrointestinal, or GI) tract, hair follicles, and mouth. This can lead to common side effects such as swollen gums, nausea, and mouth sores.

Other Causes of Mouth Sores

It is important to note that you may develop mouth sores or ulcers that are not related to methotrexate use. Other types of lesions in the mouth include:

• Cold sores — The herpes simplex virus causes these blisters, which develop on and around the lips.
• Canker sores — These shallow sores develop on the soft tissue inside the mouth and may appear red with yellow, gray, or white coloration. Unlike cold sores, canker sores are not contagious.
• Leukoplakia — This condition, which also affects the mouth’s soft tissues and causes thick, white patches, is common in those who smoke.
• Oral lichen planus — This chronic inflammatory disorder can cause raised, white patches of tissue that resemble webs on the cheeks, gums, tongue, and lips.

Note that mouth sores caused by methotrexate are not contagious and cannot be spread by kissing or by sharing food and drinks. If you are unsure of the reason for your mouth sores, ask your doctor or rheumatologist.

Managing Mouth Sores From Methotrexate

If you develop mouth sores after starting methotrexate treatment, talk with a health care provider or your rheumatology specialist. They will work with you to find a treatment or dosage that successfully manages your RA symptoms while minimizing possible side effects.

Adjusting Your Dosage

Because the mouth sores are caused by medication (rather than the RA itself), stopping or changing the dose of methotrexate can be one of the quickest ways to reduce or eliminate mouth sores or ulcers. Studies have shown that the average healing time for mouth ulcers after stopping medication is about three weeks. However, how long it takes for ulcers to clear varies from person to person.

Your rheumatologist may recommend that rather than discontinue methotrexate, you use the injectable instead of the oral form, or split your medication into two daily doses. Both approaches may help reduce side effects.

Note that you should never stop your medication or change the dosage without consulting your doctor. They will be able to determine the best regimen to treat your RA while reducing side effects such as mouth sores.

Supplementing With Folic Acid

GI-related side effects of methotrexate are caused by reduced folate levels, so supplementing your diet with folic acid can be an effective way to reduce side effects like mouth sores. According to the Arthritis Foundation, one study determined that folic acid supplements reduced the risk of mouth sores and other GI side effects by 79 percent in those taking methotrexate for RA. Your doctor will know which folic acid dosage is best for you based on the severity and frequency of your sores.

Some myRAteam members have reported success after starting supplements. “My doctor increased my dosage of folic acid, and I haven’t had any [mouth sores] since,” shared one member.

“I used to get little mouth ulcer sores from methotrexate,” wrote another member, “but now I take more folic acid tablets, and it seems to have worked.” Another shared, “I was getting oral ulcers all the time. My specialist put me on 5 milligrams of folic acid six days per week, only missing the dose on MTX [methotrexate] day. It has helped.”

Reducing Discomfort

While waiting for your mouth sores to clear up, you can take steps to ease the pain or discomfort. Saltwater rinses or specialty mouthwashes with the pain reliever lidocaine can help.

One myRAteam member asked others whether they had experienced mouth sores from methotrexate: “If you have had these, any tips or tricks while they heal?”

One member wrote that they “use alcohol-free mouth rinses” to cope with mouth sores, and another shared that they use something called magic mouthwash. “My rheumatologist would put me on it to deal with the mouth sores,” they said.

One member had similar success with this mouthwash: “I got a mouthwash called magic wash by cancer patients. The doctor prescribed it — the bottle says ‘mouthwash BLM.’ It worked well, but then I switched to injectable methotrexate.”

Other members find that sucking on mints or hard candies helps. “I use Mentos,” one member wrote. “One or two a day seems to keep the sores away.”

Consult your doctor before trying any new methods for managing mouth sores. They can help you find the best solution to manage this side effect, relieve discomfort, and continue your RA treatment.

Find Your Team

If you or a loved one is living with rheumatoid arthritis, consider joining myRAteam today. Here, you’ll find a dedicated community of over 191,000 members having struggles and experiences similar to yours — and they’re ready to help, inform, and educate on what living with rheumatoid arthritis is truly like. On myRAteam, you can share your story, ask and answer questions, and connect with others who understand life with RA.

Have you developed mouth ulcers or sores as a result of methotrexate? How have you managed them? Share your story in the comments below or by posting on myRAteam.