Pruritus: What It Means, Types and Causes of Itching

Pruritus meaning: what itching is and why it happens

Pruritus (from the Latin for "to itch") is the medical word for an itch, the sensation that makes you want to scratch. Doctors call itch acute if it has lasted under 6 weeks and chronic if it lasts 6 weeks or more. Chronic pruritus is common, especially over age 65.

Itch signals travel along special nerve fibers from the skin to the spinal cord and brain. Histamine, released in allergic reactions and hives, is one trigger, but many itches are driven by other chemicals and by nerve sensitization. That is why antihistamines help hives but often do little for other types of itch. Scratching briefly relieves itch by causing mild pain, but it also damages skin and releases more itch chemicals, creating the itch-scratch cycle.

Types of pruritus

Itching with a rash: common skin causes

If you can see a rash, bumps, welts or scaling (not just scratch marks), the cause is usually in the skin itself.

• Dry skin (xerosis): the commonest cause, especially in older adults and in winter. Skin looks rough and flaky, often on the shins.
• Eczema (atopic dermatitis): itchy, dry, inflamed patches in skin creases, often starting in childhood.
• Contact dermatitis: an itchy, red rash where the skin touched an irritant or allergen, such as nickel, fragrance, preservatives, poison ivy or latex.
• Hives: raised, itchy welts that move around and fade within 24 hours.
• Insect bites and stings.
• Scabies: intense itch worse at night, with small bumps and burrows between the fingers, wrists, waist and genitals. Spreads to close contacts.
• Fungal infections: ringworm, athlete's foot and jock itch.
• Psoriasis, lichen planus and dermatitis herpetiformis (linked to celiac disease).
• Lichen simplex chronicus: a thickened, leathery patch from repeated scratching.

Itching without a rash: internal causes

When the skin looks normal apart from scratch marks, doctors look for internal causes:

• Chronic kidney disease, especially in people on dialysis
• Liver and bile duct disease: itching often starts on the palms and soles, with or without jaundice
• Iron deficiency and polycythemia vera (itch after a warm bath is typical of polycythemia)
• Thyroid disease, over- or underactive
• Diabetes, through dry skin and nerve damage
• Medicines: opioids, some blood pressure drugs, statins, antimalarials and many others
• Pregnancy, including intrahepatic cholestasis of pregnancy
• Blood cancers, especially Hodgkin lymphoma, which can cause itching months before other symptoms
• HIV infection

Generalized vs localized pruritus

Where you itch is as useful a clue as whether there is a rash.

Common sites of localized itching

• Scalp: dandruff (seborrheic dermatitis), psoriasis, head lice and hair product allergy. See itching of the scalp.
• Upper back, between the shoulder blades: a patch of itch with a darker area of skin is often notalgia paresthetica, from an irritated spinal nerve.
• Outer forearms: brachioradial pruritus, an itch or burning in sun-exposed arms linked to neck nerve irritation and sun damage.
• Anus: moisture, hemorrhoids, irritation from wiping or soaps, and threadworms in children. See anal itching.
• Palms and soles: liver and bile duct problems, including cholestasis in late pregnancy.
• Shins: dry skin, especially in winter and in older adults.

Itching of the scrotum or groin

Genital itching in men is usually caused by sweat and friction, jock itch, yeast or a reaction to soaps and detergents. Our guide to an itchy scrotum, its causes and treatment explains how to tell these apart and how to treat each one.

How doctors diagnose the cause of itching

Your doctor will ask where the itch is, how long it has lasted, whether others at home itch, about new products, medicines, travel and other symptoms. They will examine the skin closely. For chronic itch without a clear skin cause, blood tests usually include a blood count, iron studies, kidney, liver and thyroid function, blood sugar, and sometimes HIV and hepatitis tests and a chest X-ray.

How to stop itching

At home

• Moisturize at least twice a day with a thick, fragrance-free cream or ointment, ideally within 3 minutes of bathing.
• Take short, lukewarm showers and use a gentle, soap-free cleanser.
• Cool the skin: cold compresses, calamine lotion or creams with menthol or pramoxine.
• Avoid triggers: wool, fragrances, harsh detergents, and overheating.
• Keep nails short and try pressing or patting instead of scratching.
• Humidify dry indoor air in winter.

Medicines

• Antihistamines: non-drowsy types for hives and allergy. Sedating types at night may help sleep, but avoid them in older adults when possible because they cause confusion and falls. Follow the label dose.
• Topical steroids for eczema and dermatitis, used as directed.
• Prescription treatments for chronic itch: calcineurin inhibitor creams, phototherapy, and medicines that act on nerves, such as gabapentin, certain antidepressants, or newer biologic drugs for severe eczema and prurigo.
• Treating the cause: iron for iron deficiency, adjusting medicines, or specific treatment for kidney or liver disease.

Frequently asked questions

What is pruritus?

Pruritus is the medical term for itching, the sensation that makes you want to scratch. It can be caused by skin problems such as dry skin, eczema and fungal infections, or by internal conditions such as kidney or liver disease, iron deficiency and thyroid problems.

What is the difference between generalized and localized pruritus?

Generalized pruritus affects large areas or the whole body. Without a rash it often has an internal cause, such as kidney or liver disease, iron deficiency or medicines. Localized pruritus affects one area, such as the scalp, back or anus, and usually has a local skin or nerve cause.

What does itching without a rash mean?

The most common cause is dry skin, especially in older adults and in winter. If moisturizing does not help within 2 weeks, internal causes are possible: kidney or liver disease, iron deficiency, thyroid problems, medicines such as opioids, and rarely lymphoma. A doctor can check with simple blood tests.

Why is itching worse at night?

Skin temperature rises at night, the body releases less of its natural anti-inflammatory hormones, and there are fewer distractions. Most itchy skin conditions feel worse in bed. Itch that is much worse at night and affects others in the household suggests scabies.

When should I worry about itching all over?

See a doctor if itching all over lasts more than 2 weeks without an obvious cause, keeps you awake, or comes with weight loss, fever, night sweats, tiredness, or yellow skin. These can signal liver, kidney, thyroid or blood disorders.