I use yolk on my hair sometimes. Put it in my hair and leave for couple of hours, or less or more, depending on how busy I am. It's quite messy and get's dry really quickly so you have to be quick putting it in. Put a shower cap or a towel around it to stop it drying out too quickly.
I am quite lazy and don't do it regularly but I've been doing it on and off since I was small, someone in my family used it and swore by it. I even remember seeing an Egg Shampoo somewhere once, so I think there is some goodness in it! And it's natural, rather than taking Biotin!