Itch, also known as pruritus, is an unpleasant sensation felt on the skin that causes a desire to scratch the affected area. In healthy individuals, itching can occur spontaneously because of day-to-day stimuli on the skin including stray hairs, dry weather, or encounter with an irritant in the environment. However, itching can be more pathologic too in cases of being bitten by mosquitos, exposed to poison ivy, or developing a hive reaction to a medicine. Herein, we summarize different kinds of itching across the spectrum of health and disease.
It is a common symptom of many skin conditions and its cause can range from harmless to serious. It can be caused by conditions from dry skin to an allergic reaction or a more serious underlying medical condition. Chronic itch can be roughly divided into four clinical causes:
Originates from the skin and can be caused by exposure to external allergens (e.g. mosquito bites or poison ivy) or internal itch mediators translocating to or being produced by your skin. This type of itch is often associated with skin disorders such as eczema (atopic dermatitis), chronic urticaria, or psoriasis.
Caused by an underlying medical condition such as chronic kidney disease or lymphoproliferative disorder (e.g. leukemia or lymphoma).
Results from damage along the itch pathways in your nervous system. This form of itch is seen in conditions such as spinal cord injuries, brachioradial pruritus, and prurigo nodularis.
Is not associated with any dermatologic or systemic causes. It is induced in response to the chemicals serotonin and norepinephrine, which regulate stress, depression, and delusional parasitosis (a false belief of parasite infestation).
Itch is a sensation that many people experience yet don’t understand. The philosopher Aristotle (384-322 BC) recorded one of the first known descriptions of itch, characterizing how animals scratch themselves in a manner similar to modern humans.