The smilarity between hair and egg is the protein content. Our hair is made of protein.
Have u ever seen what happen when u cook an egg? It will harden right?
That will happen to ur hair too! If u r under the sun, the water from ur hair strand will be evaporated. What happen next? Haha.. U will have dry and hard hair..
Therefore, put on some UV protecting hair product before u go out. Always use umbrella or wear hat to avoid direct sun.