An outbreak of swollen, pale red bumps or plaques on the skin is referred to as urticaria or hives. It appears suddenly either as a result of the body's reaction to certain allergens or for unknown reasons. There are several types of hives such as acute urticaria, chronic urticaria, physical urticaria, and dermatographic urticaria. Rapid edema or swelling of the area beneath the skin is known as angioedema. It is normally a result of an allergic reaction but can also be hereditary. This book brings forth some of the most innovative concepts and elucidates the unexplored aspects of urticaria and angioedema. Its aim is to present researches that have transformed this discipline and aided its advancement. This book will serve as a reference to a broad spectrum of readers.