Horse 1453 - Looking for Vitamin H

I was in the bathroom one day and whilst in there, I tend to read all sorts of things. On this particular occasion I picked up a bottle of shampoo and noticed that not only did the list of the ingredients made no sense to me whatsoever but that I had no idea what Vitamin H was, or really what a vitamin is for that matter. I was pretty sure that vitamins sort of ended when they got to E because I couldn't for the life of me, remember that there even was a Vitamin F let alone Vitamin H.
I then remembered that vitamin H did mean something too me after all but that the source that it came from wasn't really that reliable or helpful:

“It also contains vitamin C, vitamin D, vitamin E, vitamin F, vitamin G, vitamin I, vitamin J, vitamin K, vitamin L, vitamin M, vitamin N, vitamin O, vitamin P, vitamin Q , vitamin R, vitamin T, vitamin U, vitamin V, vitamin W, vitamin X, vitamin Y, and, believe it or not, vitamin Z! The only two vitamins it doesn't have in it are vitamin S, because it makes you sick, and vitamin H, because it makes you grow horns on the top of your head, like a bull. But it does have in it a very small amount of the rarest and most magical vitamin of them all — vitamin Wonka.”
- Charlie And The Chocolate Factory, Roald Dahl (1964)

Of course basing one's knowledge on a children's novel is a silly idea, but I at least saw the irony that vitamin H in this list would make you grow horns on the top of your head and shampoo is used precisely in that location. If this story in Charlie And The Chocolate Factory was fact, then you'd be well advised never to use this brand of shampoo ever again.
It still leaves my two questions of what is Vitamin H and what is a vitamin anyway?

A vitamin is a chemical which can not be synthesised in sufficient quantities by the human body and must be absorbed through the diet. This is different to an essential nutrient which can not be synthesised by the body at all and a "dietary mineral" which in terms of the human diet are the chemical elements other than carbon, nitrogen, oxygen and hydrogen which are required by the body.

There used to be a pretty long list of vitamins that all the way down to Vitamin U when for one reason or another, it was either discovered that they were either synthesised in the human body or non essential. The other problem was that Vitamin B was expanded to include a whole group of  water-soluble chemicals which  are all needed for cell metabolism. Vitamin B instead of being a single chemical was actually found to be a whole host of them.
This is where Vitamin H comes in.

Vitamin H was discovered in 1935 by Dean Burk and was named for the German words "Haar und Haut" being "hair and skin". This sounds perfectly in line which it being included in the list of ingredients in a bottle of shampoo. It was later found to be the same chemical as Bioton which had already been identfied as Vitamin B7.
Biotin is needed in the production of some  fatty acids, and the metabolism of fats and amino acids; all of which produce all sorts of useful chemicals in the human body. Also, there appears to be an anti-Vitamin called Avidin which mainly comes from egg whites which impedes the effectiveness of Biotin.

There it is then. Vitamin H is a thing but probably shouldn't be called Vitamin H because it's actually the same thing as Vitamin B7. Assuming that Mr Willy Wonka was correct in saying that Vitamin H "makes you grow horns on the top of your head, like a bull"  then the cure would be to start smashing egg whites into your scalp.
Also as a curious aside Vitamin S which "makes you sick"  is the chemical Salicylic Acid which is active ingredient in Aspirin. I don't know about it making you sick but certainly just thinking about all of this, gives me a headache.