About Itching

Itching is an unpleasant sensation that creates the desire to scratch or rub the skin. It occurs when various stimuli, such as physical or chemical contact, changes in temperature, and changes in humidity, cause excessive secretion of histamine, prostaglandins, proteases, cytokines, and so on. If the skin is repeatedly rubbed or scratched because of itching, a thick, leather-like change in the skin (lichenification) can occur. The areas around the nostrils, anus, and vulva are especially sensitive to itching. Most itching is associated with skin diseases themselves, but because it can also be related to systemic diseases and psychiatric disorders, it is important to find the exact cause and treat it.

Causes Itching can occur for various reasons. Depending on the cause, itching can be divided into itching associated with skin diseases, itching associated with systemic diseases, and itching associated with psychiatric disorders.

1. Itching associated with skin diseases Itching most commonly accompanies skin diseases. It can occur with dermatitis herpetiformis, scabies, pediculosis, insect bites, hives, atopic dermatitis, contact dermatitis, psoriasis, nummular eczema (a condition in which eczema appears in coin-shaped patches), lichen (a symptom in which the skin becomes thick and the wrinkles appear very pronounced), neurodermatitis, and others.

Winter itching occurs in more than 50% of elderly people aged 70 and older. The main cause is skin dryness resulting from reduced moisture and decreased sebum secretion due to aging of the skin, and itching often appears on the arms and shins. Anal itching is often accompanied by anorectal diseases or infections. In addition, itching of the vulva can be caused by friction, sweating, pregnancy, pads, birth control pills, vaginal douches, condom use, and so on.

2. Itching associated with systemic diseases Itching is also commonly accompanied by systemic diseases such as jaundice, chronic renal failure, malignant blood tumors, polycythemia vera, parasitic infections, hyperthyroidism and hypothyroidism, and acquired immunodeficiency syndrome. Itching occurs in 20–25% of patients with jaundice, and in patients with obstructive biliary disease, chronic liver disease, and cirrhosis, where the flow of bile is blocked, generalized itching that affects the whole body intensely is accompanied by jaundice. About 20–50% of patients with chronic renal failure undergoing hemodialysis experience itching, and in hypothyroidism, the skin becomes severely dry due to myxedema, which can lead to generalized itching. Itching is common in patients with diabetes, and in the case of acquired immunodeficiency syndrome, systemic diseases such as scabies, lice, candidiasis, seborrheic dermatitis, renal failure, and cholestasis are often present, which in turn commonly cause itching.

3. Itching associated with psychiatric disorders When a person scratches frequently because of psychological stress related to a skin disease, lichenification develops, causing the skin to become hard and thick, and this creates a vicious cycle in which itching repeats. Trichotillomania is a neurosis in which a person pulls out their hair due to an abnormal urge. It is caused by psychological and social stress, and stress at home or in social life, a sense of competition, moving, a family member being hospitalized, and family relationships can be issues. Factitial dermatitis is dermatitis that occurs when a person deliberately injures their own skin with chemicals, corrosives, fingernails, sharp tools, hot metal, and so on, in order to gain sympathy or avoid responsibility. Patients injure their own bodies to satisfy psychological needs, and they often deny or show indifference toward the fact that they caused their own lesions.

So far, I have explained itching. In the next part, we will look at the diagnosis and treatment of itching.

Source: National Health Information Portal, Korea Disease Control and Prevention Agency