Mary, mary, quite contrary
I recall hearing about hair treatments in the 50's (older sister) that involved massaging egg yolks into freshly shampooed hair. And then there were the milk baths (I think Mae West made those famous).
In the 70's I read a counter culture type book on hair care that recommended a hot oil treatment now and then. Any old vegetable oil would do.
Vinegar has always made a good hair conditioner, as it corrects the high pH of cheap shampoo. It works by helping the scales on the hair shaft, which have curled away in the high pH of most soaps/detergents, relax and lay flat against the shaft. Result is silkier, smoother hair. pH balanced shampoos appear to have done much the same thing. For that matter, fresh lemon juice is reputed not only to be a good hair conditioner, but a dandruff cure as good if not better than store-bought remedies.