What term describes severe itching?

The term that describes severe itching is pruritus. This medical term specifically refers to the sensation that provokes the desire to scratch. Itching can be a symptom associated with various skin conditions or systemic diseases, but pruritus itself is the recognized term for the sensation.

In contrast, dermatitis refers to inflammation of the skin, which can indeed include itching as part of its symptomatology, but does not solely define it. Urticaria, commonly known as hives, is characterized by raised welts on the skin and can also be itchy, but again, it is the condition rather than the pure sensation of itching. A rash is a general term for any change in the skin, such as redness or bumpiness, and can accompany various conditions including pruritus, but it is not specific to the sensation of itching itself. Thus, pruritus is the precise term to use when referring to the intense urge to scratch due to itching.