Methotrexate affects the mouth more than most people expect from a drug taken for joint pain or skin conditions. Mouth ulcers are the best-known dental side effect, showing up in roughly one in ten patients on low-dose therapy, but the list extends to taste disturbances, yeast infections, gum changes, and rare but serious jawbone complications. The good news is that most of these problems are manageable once you know what to watch for and how to respond.
Mouth Ulcers Are the Most Common Problem
Mouth ulcers, clinically called stomatitis or oral mucositis, are by far the most frequent dental side effect of methotrexate. A systematic review of low-dose methotrexate-induced oral ulcers found they appear in roughly 11% to 17% of patients on low doses, with an average prescribed dose of about 11 mg per week.1PubMed Central. Management options for low-dose methotrexate-induced oral ulcers: A systematic review A separate meta-analysis of randomized controlled trials put the prevalence of stomatitis at around 6% to 8%, depending on how studies that did not specifically report mouth ulcers were counted.2PubMed Central. Low Dose Methotrexate and Mucocutaneous Adverse Events: Results of a Systematic Literature Review and Meta-Analysis of Randomized Controlled Trials The variation between studies reflects real differences in dosing, patient populations, and how aggressively researchers looked for ulcers, but the general picture is clear: if you are on methotrexate, there is a meaningful chance your mouth will let you know.
These ulcers tend to be painful, shallow sores on the inner cheeks, tongue, lips, or gums. They look similar to common canker sores but can be larger, take longer to heal, and sometimes appear in clusters. Methotrexate works by interfering with rapidly dividing cells, which is useful against inflammatory and immune-related disease but also hits the fast-turnover lining of your mouth. That is why the oral lining is particularly vulnerable compared to, say, the skin on your arm.
In published case reports, methotrexate-induced mucositis has sometimes been severe enough to require hospitalization, particularly when it was caused by an accidental overdose or accumulated toxicity over time.3PubMed. Oral mucositis in patients receiving low-dose methotrexate therapy for rheumatoid arthritis: report of 2 cases and literature review More commonly, the ulcers are uncomfortable but resolve within a few weeks once the drug is paused or the dose adjusted.
How Mouth Ulcers Are Treated
The single most effective step is stopping or reducing methotrexate, combined with folic acid supplementation. In the systematic review of management options, the most common approach for healing oral ulcers was discontinuing methotrexate and adding folic acid, used in about 29% of cases. Simply stopping methotrexate without adding folic acid accounted for another 25%. Some patients received antibiotics or corticosteroids alongside discontinuation. Among patients whose healing time was tracked, the average was about 20 days.1PubMed Central. Management options for low-dose methotrexate-induced oral ulcers: A systematic review
Folic acid supplementation deserves extra attention because it sits at the center of both prevention and treatment. Methotrexate works partly by blocking folate metabolism, and folate is essential for DNA synthesis in rapidly dividing cells, including the ones lining your mouth. Most rheumatologists now prescribe folic acid alongside methotrexate from the start to reduce side effects, typically 1 mg daily or 5 mg once weekly on a non-methotrexate day. If you are not already taking supplemental folic acid with your methotrexate, that is the first conversation to have with your prescriber.
For pain relief while ulcers heal, topical options include lidocaine-based rinses and compound mouthwash formulations (sometimes called “magic mouthwash,” a mix that varies by pharmacy but usually includes a local anesthetic, an antacid coating agent, and sometimes an antihistamine). In at least one reported case, magic mouthwash was insufficient for controlling pain in severe mucositis, and a morphine-based mouthwash solution was used instead.4PubMed. Effective Treatment of Methotrexate Induced Oral Mucositis With a Morphine Mouthwash Solution: A Case Report That is an unusual scenario, but it illustrates that severe cases sometimes require more aggressive pain management than over-the-counter options can provide.
The Vicious Cycle of Painful Mouths and Poor Nutrition
One underappreciated problem with methotrexate-related mouth ulcers is how they can make themselves worse. Painful sores make eating difficult, which leads to poor nutritional intake, which in turn lowers folic acid levels further, which worsens the oral ulcers.5PubMed Central. Management options for low-dose methotrexate-induced oral ulcers: A systematic review – Section: Discussion If you notice mouth sores developing and you start avoiding food because it hurts to chew, this is a signal to contact your doctor promptly rather than waiting for the ulcers to resolve on their own. Soft, nutrient-dense foods and continued folic acid supplementation can help break the cycle.
Taste Changes
A metallic or sour taste in the mouth is a less common but real side effect. In older studies of psoriasis patients taking moderate doses of methotrexate, a metallic taste was reported by roughly 0.5% to 3% of patients, and one patient in a separate study described a persistent sour taste.6Clinical and Experimental Dermatology. Methotrexate‐induced impairment of taste acuity These numbers make taste disturbance seem rare, but it may be underreported because many patients do not think to mention a funny taste to their doctor. The effect appears to be dose-related and reversible when the drug is stopped or the dose lowered.
If you are experiencing persistent taste changes on methotrexate, it is worth mentioning at your next appointment even if it seems minor. Taste alterations can reduce appetite and enjoyment of food, contributing to the same nutritional concerns described above. There is no specific treatment beyond dose adjustment, but knowing the drug is the likely cause can at least spare you unnecessary dental investigations for a problem that is systemic rather than local.
Gum Health and Periodontal Effects
Rheumatoid arthritis and periodontal disease share underlying inflammatory pathways, so researchers have looked at whether methotrexate therapy helps or hurts the gums. The answer is mixed but leans toward “not much help.” One study found that methotrexate treatment did not result in improvement of periodontal measures even though it significantly improved the arthritis itself, as measured by standard disease activity scores and inflammatory markers.7PubMed Central. Effect of Anti-Rheumatic Treatment on the Periodontal Condition of Rheumatoid Arthritis Patients The researchers concluded that anti-rheumatic treatment with methotrexate had negligible influence on periodontal condition.
A prospective study that tracked patients starting methotrexate for six months found no significant improvement in most periodontal measurements, and actually observed a significant increase in bleeding on probing, a clinical indicator of gum inflammation.8PubMed Central. Methotrexate and Non-Surgical Periodontal Treatment Change the Oral–Gut Microbiota in Rheumatoid Arthritis: A Prospective Cohort Study A review also noted that when methotrexate was combined with TNF-inhibitor biologics, gingival inflammation could increase.9PubMed. Impact of treatment of rheumatoid arthritis on periodontal disease: A review
The practical takeaway is that being on methotrexate does not give your gums a free pass. If anything, you should be more attentive to gum health, not less. Regular dental cleanings and good brushing and flossing habits remain important, because the drug is not doing that work for you even though it is tamping down systemic inflammation.
Oral Yeast Infections
Methotrexate is an immunosuppressant, which raises reasonable concern about oral thrush and other yeast infections in the mouth. The evidence here is more nuanced than you might expect. A hospital-based cohort study of rheumatoid arthritis patients found that about 31% of those evaluated had oral candidiasis during follow-up, but when the researchers analyzed which drugs were actually driving the risk, methotrexate was not a significant predictor. The strongest predictors were prednisone and tocilizumab. The study found that most candidiasis cases were subclinical, meaning Candida was present on lab testing but the patient had no visible mouth lesions.10The Open Rheumatology Journal. Oral Candidiasis in Patients with Rheumatoid Arthritis: A Hospital-Based Cohort Study
A separate study looked at whether systemic methotrexate promotes drug-resistant yeast strains in the mouth. The findings were reassuring: yeast strains from patients on methotrexate were no more resistant to fluconazole (the most commonly prescribed antifungal) than those from a control group. Resistance rates were low in both groups.11PubMed Central. Does Systemic Methotrexate Therapy Induce Azole Resistance among Endogenous Candida Strains?
So while being on any immune-modulating regimen warrants some vigilance for thrush, methotrexate alone appears to be a lesser culprit than corticosteroids or certain biologic drugs. If you are taking methotrexate alongside prednisone and you develop white patches, redness, or a cottony feeling in your mouth, that is worth reporting. If you are on methotrexate alone, the risk of oral candidiasis is lower but not zero.
Jaw Osteonecrosis
Osteonecrosis of the jaw, where a patch of jawbone becomes exposed and fails to heal, is most famously associated with bisphosphonate drugs used for osteoporosis. Methotrexate has been linked to this condition in a small number of case reports, which makes it a genuine concern even if it is rare. A systematic review found that all described cases occurred in patients with rheumatoid arthritis, and only about 40% of those patients were also taking bisphosphonates. The patients tended to be over 60 and had been on methotrexate for more than 12 years on average. Antibiotics alone did not resolve the jaw lesions; stopping methotrexate was necessary, and healing took several months. Half of the cases required surgical coverage of the exposed bone with a mucosal flap. No recurrences were observed for at least two years after healing.12PubMed. Possible association of methotrexate use with osteonecrosis of the jaw: Systematic review
Two additional cases were reported in patients with long-standing arthritis treated with methotrexate alone, without bisphosphonates or other medications typically associated with jaw osteonecrosis.13Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. Methotrexate-associated osteonecrosis of the jaw: A report of two cases The overall number of reported cases remains small, so the direct role of methotrexate is still uncertain. But if you have been on methotrexate for many years and notice a persistent area of exposed bone in your mouth, particularly after a dental extraction, take it seriously and seek evaluation quickly.
Dental Extractions and Surgery While on Methotrexate
One of the most practical questions patients have is whether they need to stop methotrexate before having a tooth pulled or other oral surgery. A scoping review of complications after invasive oral procedures in patients on immunosuppressive medications found that most reported complications involved patients with rheumatoid arthritis on methotrexate or anti-TNF drugs. The complications included delayed healing, local infection, and medication-related osteonecrosis, and they occurred predominantly after tooth extractions, especially in women over 50 who also had bisphosphonate use, diabetes, or unhealthy lifestyle habits.14PubMed Central. Complications of invasive oral procedures in patients with immune-mediated inflammatory disorders treated with biological and conventional disease-modifying antirheumatic drugs or glucocorticoids: a scoping review of the literature
The question of whether to pause methotrexate around dental surgery does not have a universal answer. A survey of French dentists found that most patients on immunosuppressive drugs were managed without stopping treatment, and pre- and postoperative antibiotics were prescribed to more than three-quarters of patients. When the immunosuppressive was stopped, that decision was made by the prescribing physician, not the dentist.15PubMed Central. Management of dental care of patients on immunosuppressive drugs for chronic immune-related inflammatory diseases: a survey of French dentists’ practices Current rheumatology guidelines generally lean toward continuing low-dose methotrexate for routine procedures, because the risk of a disease flare from stopping the drug often outweighs the modest increase in surgical complications. But the decision depends on your specific situation, including what dose you take, what other medications are in the mix, and how complex the dental procedure is. The key is to make sure your dentist and your prescribing doctor communicate before the procedure rather than each assuming the other has it covered.
Watch Out for NSAID Interactions
Dentists commonly prescribe nonsteroidal anti-inflammatory drugs like ibuprofen for pain after procedures, and many people take them on their own for everyday aches. If you are on methotrexate, this combination deserves caution. A study of rheumatoid arthritis patients found that concurrent use of methotrexate and NSAIDs was associated with a 40% higher risk of any serious adverse event, including significantly increased risks of acute kidney failure and low blood cell counts.16PubMed. Concomitant use of low-dose methotrexate and NSAIDs and the risk of serious adverse events among patients with rheumatoid arthritis
The mechanism is straightforward: NSAIDs reduce blood flow to the kidneys, which slows the clearance of methotrexate from your body, effectively raising your methotrexate levels. Higher methotrexate levels mean more toxicity, including to the mouth. This does not mean you can never take ibuprofen, but it does mean you should tell your dentist you are on methotrexate so they can choose a pain relief option that does not compound your risk. Acetaminophen is generally considered safer in this context, and your prescribing physician can advise on what is appropriate for you.
Tablets Versus Injections in Children
Methotrexate is also used in children with juvenile idiopathic arthritis, and the route of administration makes a meaningful difference to oral side effects. A study comparing tablet and injectable methotrexate found that the oral tablet form was associated with substantially higher rates of mouth ulcers: 24% for tablets compared to about 9% for subcutaneous injections.17Journal of Clinical Pediatrics. Factors Affecting Adverse Effects Of Methotrexate In Juvenile Idiopathic Arthritis The same study found that children with poor medication compliance had nearly double the incidence of side effects compared to those with good compliance, suggesting that irregular dosing may contribute to toxicity spikes.
For parents managing a child’s methotrexate therapy, switching from oral tablets to subcutaneous injections is worth discussing with the prescribing doctor if mouth ulcers are a recurring problem. Injections bypass the gastrointestinal tract entirely, reducing direct exposure of the oral and gut lining to the drug. This also tends to reduce nausea, another common complaint in pediatric patients.
What to Tell Your Dentist
If you are taking methotrexate, your dentist needs to know, and not just in the “list your medications” sense. Several specific things change about how your dental care should be handled:
- Before extractions or surgery: Your dentist should contact your rheumatologist or prescribing physician to decide whether to continue, pause, or adjust methotrexate and whether prophylactic antibiotics are warranted.
- Pain management choices: NSAIDs like ibuprofen carry extra risks when combined with methotrexate. Your dentist should choose alternatives or consult your prescriber about safe options.
- Monitoring for unusual healing: Delayed healing after oral procedures, persistent exposed bone, or wounds that do not close on schedule should be flagged early rather than watched passively.
- Oral hygiene support: Because methotrexate does not improve your periodontal health and may slightly worsen gum bleeding, a more aggressive preventive care schedule with more frequent cleanings may be appropriate.
Many dentists are less familiar with methotrexate than rheumatologists and dermatologists are. Coming to your appointment prepared with this context helps ensure nothing falls through the cracks between specialists. If you have been on methotrexate for more than a few years, keeping a brief record of any oral side effects you have noticed, when they occur relative to your dosing day, and what has helped can be valuable at both your dental and rheumatology appointments.
High-Dose Versus Low-Dose Realities
Most of the evidence discussed here applies to low-dose methotrexate, the kind prescribed weekly for conditions like rheumatoid arthritis, psoriasis, and Crohn’s disease. High-dose methotrexate, used in cancer treatment, causes much more severe and frequent oral mucositis, and the management strategies differ. In high-dose protocols, leucovorin (folinic acid) rescue is given on a strict schedule after methotrexate infusion to limit toxicity. Research on high-dose regimens has shown that delaying this rescue beyond 36 to 42 hours from the start of the infusion leads to substantially increased toxicity.18PubMed. How long can folinic acid rescue be delayed after high-dose methotrexate without toxicity?
For low-dose patients, the parallel lesson is less dramatic but still relevant: folic acid supplementation works best as a preventive measure taken consistently. If you skip your folic acid for a week or two because you ran out or forgot, and then develop mouth sores, restarting it promptly alongside a conversation with your doctor about whether to pause methotrexate is the right move. The goal is to avoid ending up in the kind of deficit that turns a mild side effect into a painful, slow-healing problem.