Itch

Itching (pruritus) is a distressing symptom of many skin diseases, as well as systemic, neurological or psychosomatic disorders. Itching is the sensation defined as the reflex or desire to scratch the skin. Chronic itching has a similar impact on the quality of life as chronic pain. The pathophysiology of itch is implicated in the mechanisms and pathways that are described for pain. Itch is caused by a number of inflammatory chemical mediators in the skin and blood, with involvement of peripheral, as well as central neural mechanisms. Some dermatoses, such as atopic dermatitis, urticaria and lichen planus, are characterized by itch. Itching can be associated with systemic diseases, including renal failure, hepatic disorders, thyroid dysfunction, infections, haematological malignancy and solid tumours. The treatment should be directed at the underlying cause, guided by the history, clinical examination and laboratory findings. Treatments include topical corticosteroids, oral antihistamines, opioid antagonists and phototherapy. The management can be complex and no single therapy is consistently effective. This article summarizes the common causes of itching, including those associated with a rash, with normal skin or skin that has the signs of scratching. Common systemic causes of itch are also discussed with possible treatment options.