One good example of allegory in Nathaniel Hawthorne's The Scarlet Letter is Hester Prynne's daughter, Pearl.
A Pearl is a rare stone that can only be created under unique circumstances, is hard to find and, to some, represents bad luck. Similarly, a pearl is still a beautiful, white stone often used to represent purity and peace.
As we know, Pearl is a child of sin. She is the product of the affair between Reverend Dimmesdale and Hester Prynne. She, therefore, is the eternal reminder of the cause of Hester's shame. Pear is a rather difficult child in that her intellect seems quite aware of her surroundings, and she is definitely quite perceptive of her mother's internal turmoil almost as if she could read Hester's mind. There is something rare, unique, and almost supernatural about Pearl that would deem her name allegorical. Her role in the lives of Dimmesdale and Hester is equally unique. She is the shiny jewel hidden in the middle of the two. Just like a Pearl, she remains hidden from the world, as part of the punishment of isolation that her mother receives.
Therefore, Pearl is a symbol of guilt, shame, sin, but also of the passion once felt by her parents in a moment of supreme indiscretion. Her existence is as rare as her name implies. She may have been considered a curse in Hester's life but, in reality, she is Hester's blessing. All these things make a good allegory for Pearl and her role in the story.