Skin reactions and skin diseases are the main causes of itching. There are numerous triggers that can cause itching.
Dry skin is a main trigger for itching, but particularly severe itching occurs in the case of chronic or acute skin diseases. These include atopic dermatitis and psoriasis, for example. In these cases, itching generally occurs together with eczema/rashes.
Metabolic disorders such as diabetes mellitus can also cause itching.
The care/treatment of itching (pruritus) basically depends on the underlying cause.