Itch is a common skin sensation. Like pain, itch is a part of response by the nervous system to detect and process harmful stimuli from the environment. Unlike pain which elicits a reflex withdrawal, itch leads to a scratch reflex. Although scratching provides temporary relief and occasional pleasure, chronic itch and scratch can leads to worsening of underlying skin condition.
Itch is seen in many skin conditions such as atopic dermatitis, eczema, topical steroid withdrawal syndrome, psoriasis, and insect bites. Furthermore, itch in skin is associated with many systemic diseases such as chronic renal disease, gallbladder disease, liver disease (e.g., chronic hepatitis C), HIV, postherpetic neuralgia, multiple sclerosis. For many patients, chronic itching often is the number one complain. Itching is not just a mere skin irritation, it can have debilitating effects such as causing sleep impairment, anxiety and even leading to clinical depression. For many patients they often prefer pain then suffering from chronic itch.
We will devote this blog to discuss and outline four clinical classifications of itch. We hope to cover current understanding about itch. In later series, we plan to explore different ways to evaluate itch symptoms and discuss current management of itch.
Pruritoceptive itch: this describes itch originating in the skin due to skin damage, dryness or underlying inflammation. Clinical examples of this type of itch are eczema, insect bites, and urticaria.
Neuropathic itch: as the name suggests, itch in this category arise from disease or pathology located along the afferent nerve. The nervous system is divided into peripheral and the central nervous system. In the peripheral nervous system, the afferent nerve carries stimuli and signal from the skin into the spinal cord. Damage or disease in the afferent nerve bundle or the neurons can present as itch. One classic example of neuropathic itch is seen in patients who suffered from post herpetic neuralgia and the multiple sclerosis
Neurogenic itch: this is defined as itch originating centrally. Clinical example include itch from gallbladder disease.
Psychogenic itch: in this case, itch is not due to any physical illnesses but the symptom is derived from psychological or psychiatric go disorders. One classic clinical example is the delusional state of parasitophobia. Patients with this diagnosis believe they have a parasites infestation. They scratch an itch the skin try to remove the infested organisms.
The classification provides a framework for clinicians and research to understand mechanism of itch and more importantly create better treatment options for the patients. Often time, more than one classification can coexist.
Please share this post or sign up the newsletter to receive new updates.