What causes chronic itching? - Causes of chronic pruritus Chronic itching, also known as chronic pruritus, affects more people than is often assumed. Current studies show that up to 17 % of adults are affected. The lifetime prevalence is even around 25 %, and up to 36 % of patients in dermatology practices report itching symptoms. These figures illustrate the extent of the disease. In order to be able to treat chronic pruritus, it is of central importance to first find the cause, which is often not at all trivial, as the causes are manifold and are often underestimated. While the general public initially associates the symptom of itching with infectious or parasitic diseases, in everyday clinical practice there are usually other underlying triggers. The main causes include
Dermatological diseases: z. e.g. neurodermatitis or psoriasisSystemic and neurological causes: Liver and kidney diseases or nerve damage.Psychological factors: These play less of a role than is often assumed.Multifactorial correlations: Pruitus is often triggered by several causes Particularly in the case of chronic pruritus, i.e. pruritus that lasts longer than six weeks, an itch-scratch vicious circle develops. As a result, the original disease that triggered the itching recedes into the background and the diagnosis becomes even more difficult. The pathophysiology of itchingThe development of itching is a highly complex process, which we have therefore simplified here. The cutaneous nerves, the spinal cord and the brain play a central role. The fine nerve endings in the skin register stimuli and transmit them via the spinal cord to the thalamus, where the itch is perceived as unpleasant. The somatosensory cortex then processes the signals and the cerebellum finally triggers the motor reaction - scratching occurs. However, in order for our fine skin nerves to perceive a signal, there are two main ways in which itching develops in the skin:
Histaminergic pathway: This only affects about 5 % of the receptors and is mediated by histamine, which is released from the mast cells.Non-histaminergic path: This is particularly relevant in chronic pruritus. Cytokines such as IL-4 or Il-31 play a central role here. Modern therapies specifically target this mechanism. This pathway is also the focus of research. The aim is to identify more receptors and cytokines that can be influenced by targeted therapies. The vicious circle of scratchingThe skin nerves are stimulated by various stimuli. This is a physiological reaction and enormously important for our everyday perception via the skin as a sensory organ. However, prolonged scratching can trigger an overactivity of these fine nerves. Researchers have even succeeded in making these skin changes visible in skin samples. However, neuroanatomical changes occur not only in the skin, but also in the spinal cord, as a result of which other stimuli are also perceived as itching. But that's not all, because our brain is also of central importance in the itch-scratch cycle. Here the itch signals are further amplified and the reward system is activated by the scratching. This activation makes it very difficult or even impossible to refrain from scratching, because the brain rewards scratching with "happiness hormones" every time. All of the above factors and many more lead to a vicious circle in which the urge to scratch becomes increasingly compulsive, and effective treatment requires professional help. Talking to specialists and other sufferers offers valuable support. Treatment and therapyTreatment of chronic pruritus is individual and requires patience. A step-by-step therapy regimen is used, ranging from topical treatments to systemic approaches. Newer medications, such as biologics, show promising results and it is important to provide those affected with comprehensive information about the disease and treatment options. Guidelines, for example from the AWMF, offer evidence-based instructions for doctors*
inside and patient*and are updated regularly. Here is the link to the guidelines, you are welcome to inform yourself!
https://register.awmf.org/de/leitlinien/detail/013-048