Chemically speaking, when baking soda and vinegar (of any sort) combine, they form carbonic acid which does very little in the way of cleaning hair. Also, because it's a chemical reaction, it will cause some heat which will only add to any dryness (which would increase itching) and fuzziness problems that you may be having. The reason they work so well separate, is because the vinegar dissolves all extra baking soda residue. Since baking soda is a type of salt it can cause extreme dryness, itchy and flaky scalp, and in high enough concentrations (of salts that is) can eat little holes into your scalp. The vinegar makes sure that all that salt is dissolved, and moisturizes your hair while it's restoring the ph balance to your scalp.I bet it's the tea tree oil and the cold water rinse that's helping more than anything. Tea tree oil is good for all kinds of stuff. As a matter of fact, I've been using it to help with pimples on my face....works like a charm!I'm not sure about drains, but I do know that this works on my scalp really well, even without the tea tree oil.
Sister Rags said: Some say it does, I say it does not. Mixing the 2 + tea tree oil is a remedy I've been using since I was a kid a gazzilion years ago. I figure, if it clears drains, it'll fix scalp problems ; )