+1. 215.677.3060 info@iacdworld.org

International Academy of Cosmetic Dermatology

ITCHING

Itching (pruritus) is a sensation that produces the desire to scratch; it is exclusive to the skin and the cornea. Teleologically, itching, with resultant scratching, is of possible biological value in combating parasitic infestation.

Pruritus probably originates in the specialized fine afferent unmyelinated C fibers located close to the dermal-epidermal junction. This sensation is transmitted via the lateral spinothalamic tract to the thalamus and to the sensory cortex. It is mediated by the release of a variety of chemical substances:  histamine, seritonin, tryptase papain, and probably substance P.

There are several types of itching:
  • Pruritoceptive itching arises in the nerve fiber endings due to skin damage such as dryness or inflammation.
  • Neuropathic itching is due to a disease in the afferent pathway; i.e. herpes zoster neuropathy.
  • Central or neurogenic itching is perceived as occurring in the skin, but it actually originates in the central nervous system due to dysfunctional processing of sensory information in the central pathways.
  • Psychogenic itching is either localized or generalized itching, but it is a skin manifestation related to a psychological disturbance.

Thus, itching is a predominant symptom of skin diseases and a frequent manifestation of systemic or psychogenic diseases.  Itching, associated with  skin diseases, is usually accompanied by a distinctive eruption (lichen planus, psoriasis, urticaria etc) but not always (atopic dermatitis, pre-bullous pemphigoid, etc.).  In systemic diseases that causes itching, such as liver disease, uremia , hypo and hyperthyroidism, and iron deficiency anemia, the only skin findings may be excoriations due to scratching scratching. It is noteworthy that several malignant diseases are sometimes accompanied by severe pruritus and even skin burning: polycythemia vera, lymphoma (especially Hodgkin’s disease), leukemia, myeloma, carcinoid, and other internal malignancies.  Other common forms of itching include senile pruritus and drug-induced itching.

Batya Davidovici, MD
Ronni Wolf, MD
Rechovot, Israel

To print, please download this PDF file