There are many causes of itching. General itching may be a symptom of many conditions including:

• diabetes (Type 1 and 2),
• thyroid disease (hyperthyroidism),
• some conditions affecting your liver (including primary biliary cirrhosis, liver cancer, hepatitis),
• a condition affecting your kidneys (chronic renal failure), and
• iron deficiency anemia.

Other common causes include:

• skin conditions, such as eczema, psoriasis, lichen planus and rosacea,
• an infection, such as chickenpox or scarlet fever,
• an intense itch of a particular part of your body may be due to the presence of lice (body lice, head lice, pubic lice),
• a skin infection caused by a tiny mite (scabies),
• anal itch, this is common and may have many causes, including threadworms and hemorrhoids (piles),
• a fungal infection (tinea), which can lead to itching between the toes (athlete's foot), in the groin (jock itch) or on the body (ringworm),
• candidasis, which can cause itching in the external genitalia in women,
• obstetric cholestasis in pregnancy, itching during pregnancy is common, but should be checked out by your doctor, especially in the third trimester (as it leads to stillbirth),
• insect bites and stings, which may cause localized itching and skin irritation,
• sunburn or dry skin, and
• prickly heat, which is a very itchy rash that appears in hot, humid weather.

Itching can be caused by a reaction to a medicine, or an allergy to many things, including cosmetics or fabrics, contact with certain metals (such as nickel), or contact with poisonous or stinging plants. The itchy red welts of hives (urticaria) on the surface of the skin are usually an allergic reaction to food or medicine.