“Do the soup thing,” he said. “That’s better than forcing air into your nose.”

Ingesting colloidal silver

Many claims about the benefits of colloidal silver come from companies that sell the product.

Colloidal silver comes in different forms — often as a bottled liquid with silver particles — and is promoted as a dietary supplement. But according to the National Center for Complementary and Integrative Health, evidence about the medical benefits are lacking, and silver can be harmful. One possible side effect is a condition called argyria, a blue-gray skin discoloration. Colloidal silver could also hinder the absorption of some drugs.

Last week, the Food and Drug Administration said that it had warned seven companies to stop selling products, including colloidal silver, that the companies suggested cure or prevent the coronavirus.

Getting some sun

It is not yet known what effect sunlight or ultraviolet light has on the new coronavirus. And if the virus is already reproducing inside of a human body, ultraviolet light — from the sun or from a lamp — can’t reach it.

A walk in the sunshine might be good for your mental and physical health if you practice social distancing. And there is evidence that ultraviolet light can inactivate viruses, including flu viruses, particularly in laboratory settings.

The W.H.O. warns, however, that ultraviolet light lamps should not be used to sterilize hands or other body parts because they can irritate the skin.

Taking your vitamins

Social media is full of suggestions about taking additional vitamins — C is a popular one — and ingesting things like garlic, pepper, mint or elderberry. But there is little evidence that these foods and supplements can protect you in any consistent or significant way.