I saw a social media post today passing on the idea that inhaling steam could protect against COVID-19. By steam, I think it is safe to assume that it means the warm mist that comes from a hot liquid that is cooling and not water excited into its gaseous form at 100°C. Even so, the kinds of proteins that make up humans start to denature just as surely as viruses when you heat them towards 60°C and beyond; what I’ve learned from the appliance of heat for cooking makes me very cautious about claims for the appliance of heat for a cure.

Breathing in steam has long been regarded as a home remedy for congestion-causing diseases like the common cold. However, studies have suggested that it is ineffective (Forstall et al., 1994). The benefits that derive are probably partly placebo (belief in the treatment), partly side-effects (sweating and other responses to bring temperature down causing your nose to run and temporarily clear) and partly due to other factors that may be introduced, such as drops of a decongestant like Olbas Oil.

I read around a fair amount before posting a short response back and there wasn’t as much clear cut information as I would have liked. I found the claim in various forms and also fact-checking sources debunking it going back almost a year but less hard evidence that I really wanted. I even found a very recent paper suggesting it is worth further investigation (La Marca et al., 2021). However, it should be noted that this was based on a very small sample size and they don’t suggest it should be immediately pushed as a public health treatment before much further research.

My final thought on the matter is that, as well as being unsubstantiated, the claim is also costly and risky. The cost is that you would have to find the time to indulge in at least a daily steam inhalation and probably several. The risk is that you cook your nasal lining or scald yourself (or someone else) in the process. I think I’ll stick with staying home most of the time, wearing a mask when around other people and getting my vaccination when I get the chance: prevention rather than cure.