itching and dermatitis
skin disorders
Itching
Itching can result from Skin disorders Disorders of other organs (systemic disorders) Disorders of the nervous system Psychologic disorders Drugs, medications, and chemicals In many skin and systemic allergic disorders, itching is caused by histamine. Histamine is a chemical in the body that is stored in mast cells. Mast Cells are part of the Themost common causes of itchingare skin disorders: Dry skin (see Dry Skin (Xeroderma) and Atopic Dermatitis (Eczema) (sometimes called eczema) Allergic contact dermatitis (an allergic rash resulting from direct contact with a particular substance) Hives (can be caused by a variety of skin or systemic conditions or drugs and chemicals) Overview of Fungal Skin Infections None Parasitic skin infections (such as Scabies Infestation ) Insect Bites None Several systemic disorders can cause itch without any visible changes on the skin (such as a rash). Systemic disorders are less common causes of itch than skin disorders. Some of themore common systemic causes of itchingare Chronic Kidney Disease None Diabetes Mellitus (DM) None Disorders of the liver or gallbladder, particularly when they cause Jaundice in Adults None Hyperthyroidism (an overactive thyroid gland) Hypothyroidism (an underactive thyroid gland) Less common systemic causes include Overview of Leukemia and Irritation of sensory nerves, for example, when a nerve is compressed, can cause itching localized to the part of the body supplied by that nerve. In contrast, some disorders that affect the nervous system may cause widespread (generalized) itching because itch neurons (one type of nerve cell) are too active or are less inhibited by other neurons. For example, in Multiple Sclerosis (MS) , nerve conduction is impaired because of an autoimmune process where the immune system attacks the fatty tissue that coats nerve fibers (myelin). This process makes the itch neurons less inhibited and thus more active. Itch that results from nervous system disorders is called neuropathic itch. Some people who have psychologic disorders may have itching for which no physical cause can be found. This type of itching is called psychogenic itching. Drugs, including medications, and chemicals can cause itching when taken internally or when applied to the skin. Usually the itching is caused by an allergic reaction. and some Procedure for CT used when taking certain x-rays, can also cause itching without causing an allergic reaction. 