What Causes Itchy Skin?
What is pruritus?
Pruritus can be best defined as a sensation that leads to the desire to scratch. It is important to make a distinction between chronic and acute pruritus. All humans experience the acute form for a limited amount of time during the course of life, such as the itch related to acute insect bite reaction or skin irritation. Chronic pruritus, which is defined by the International Society for the Study of Itch (IFSI) as itch that persists for 6 weeks and longer. It has a significant impact on the quality of life of millions of patients worldwide.
What you should be alert for in the history
It is imperative to determine whether the cause of chronic itch is related to a primary skin disease or secondary to a systemic disease. If a patient constantly scratches, secondary skin lesions can develop. These include:
- Prurigo nodules
- Hyperpigmentation or hypopigmentation
- Butterfly sign – normal appearing skin in the middle of back outlined by a butterfly pattern of hyperpigmentation associated with repetitive scratching.
Generalized pruritus differs from localized pruritus. A patient with localized pruritus may have other sensory complaints such as burning sensation, the loss of sensation or hypersensitivity, as well as dermatomal distribution of pruritus. These should be evaluated carefully regarding possible neuropathic itch. In generalized pruritus one should obtain a careful history including drug intake, whether other family members are itching (scabies) and if there are other systemic complaints such as weight loss, night sweats.