It’s a treatment, not a cure, of course. And I’m not even sure it’s a treatment.
Precisely why it isn’t a cure is explained by a report syndicated in the June 23, 1942 edition of the Fitchburg (Massachusetts) Sentinel:
No One Cure for Sniffles
Or in other words, there is no one cure for aggravated sniffles. — Manchester Guardian.
Coryza is a contagious inflammation of the upper respiratory tract, which is to say, a cold.
Beyond that, would this do anything interesting? Tough to say. While baking soda rinses are often helpful with mouth sores, it’s less than clear that anything you can gargle with will reach the portions of your throat that are inflamed during post-nasal drip, given that the act of gargling is calculated to keep the fluid out of your throat. So we don’t really need to get into a deep analysis of the merits, real or imagined, of baking soda in this application, because it’s never going to reach the site of the irritation.
From a box sold in Quincy, Massachusetts.
Grandma’s Cure For Sniffles
1/2 teaspoon of soda mixed with the juice of one lemon in a glass of water.
1/2 teaspoon of it mixed with a half glass of water, gargled several times a day, brings sore throat relief.