Dear Dr. Roach: I’m interested in consuming dimethylsulfoxide (DMSO). I’ve read it will destroy the root of cancer and hasten the healing of broken bones, ligaments and strained muscles. My question is whether it is OK to consume the suggested amount of DMSO?

My aortic valve was replaced with a mechanical valve three years ago. After 12 months of follow-up exams, I was informed that the valve had sealed perfectly and was told to enjoy life.

— W.H.

Answer: DMSO is indicated by the Food and Drug Administration for the symptomatic relief of interstitial cystitis, a chronic and painful bladder condition. It is instilled directly in the bladder for this and is sometimes used for other urinary conditions, although there is no evidence of its usefulness.

DMSO is often used topically for musculoskeletal injuries, and some people do note pain relief. Numerous studies on rheumatological conditions, such as rheumatoid arthritis, failed to show a benefit, although a study from Germany in 1995 showed that DMSO gel with a 25% concentration reduced pain when applied to joints. Other studies were unable to confirm this.

For cancer, there are no convincing studies showing benefit, and some studies have shown an increase in breast-cancer cell growth with DMSO.

Based on studies showing minimal benefit and potential harm, I recommend against the use of DMSO. What’s more important is that the studies have been done with medical-grade DMSO, which is only available with a prescription. When you buy DMSO at a hardware store, you are getting industrial-grade DMSO, which is potentially contaminated with industrial toxins and isn’t intended for human use.

DMSO is very good at bringing other substances with it into the skin. This is useful as a drug-delivery system but dangerous when the DMSO you use is contaminated with dangerous chemicals — or if you have those chemicals on your skin. While I can find DMSO for sale that companies purport to be very pure, you are relying on the company that may or may not have purified it, as it isn’t independently tested.

However, I do not think that the topical use of DMSO is likely to be a danger to your prosthetic heart valve.

Dear Dr. Roach: Recently, at an event sponsored by our community, an expert on the gut microbiome gave a lecture on how to keep it in balance. While the lecture was generally informative and useful, at one point, he stated that vaccines were detrimental to the microbiome. Is there any evidence (other than anecdotal) that supports such an opinion?

— W.G.

Answer: The huge number of bacteria in our gastrointestinal tract is referred to as the microbiome, and our microbiome can have effects on many aspects of our functioning. How much of an effect it has is debated.

COVID-19 infections were known to have a marked detrimental effect on the microbiome, but the effect of vaccination on the microbiome was not well-studied until quite recently. A 2024 study from the University of Cambridge found that the microbiome was only minimally affected by vaccination. Based on this recent study, I disagree with your community speaker and conclude that if your concern is about your microbiome, you’d be much better off getting vaccinated and taking other steps to prevent infection.

Contact Dr. Roach at ToYourGoodHealth@med.cornell.edu.