Itch - Causes

Causes

Infections and infestations:

• Allergic reaction to contact with specific chemicals, such as urushiol, derived from poison ivy or poison oak.
• Body louse. Body lice can be seen in substandard living conditions.
• Cutaneous larva migrans.
• Head lice, if limited to the neck and scalp.
• Herpes.
• Insect bites, such as those from mosquitos or chiggers.
• Photodermatitis – (sun) light reacts with chemicals in the skin, leading to the formation of irritant metabolites.
• Pubic lice, if limited to the genital area.
• Scabies especially when several other persons in close contact also itch.
• Shaving, which may irritate the skin.
• Swimmer's itch
• Varicella (Chickenpox) Most common in young children. Highly contagious.

Environmental and allergic:

• Urticaria (also called hives) usually causes itching.

Dermatological disorders:

• Dandruff. (An unusually large amount of flaking is associated with this sensation.)
• Scab healing; scar growth; and the development or emergence of moles, pimples and ingrown hairs from below the epidermis.
• Skin conditions (such as psoriasis, eczema, sunburn, athlete's foot, hidradenitis suppurativa and many others). Most are of an inflammatory nature.
• Punctate palmoplantar keratoderma.
• Xerosis (dry skin). This is the most common cause, frequently seen in the winter and also associated with older age, frequent bathing in hot showers or baths, and high-temperature and low-humidity environments.

Medical disorders:

• Diabetes Mellitus.
• Hyperparathyroidism.
• Iron deficiency anemia.
• Jaundice and Cholestasis. (Bilirubin is a skin irritant at high concentrations.)
• Malignancy or internal cancer such as lymphoma, Hodgkin's disease.
• Menopause or changes in hormonal balances associated with aging.
• Polycythemia, which can cause generalized itching due to increased histamine.
• Thyroid illness.
• Uraemia.

Medication:

• Directly (e.g. morphine and other opiates)
• Chloroquine.

Related to pregnancy:

• Gestational pemphigoid
• Intrahepatic cholestasis of pregnancy
• Pruritic urticarial papules and plaques of pregnancy (PUPPP)
• Psychiatric disease.