Itchy skin is a symptom doctors refer to as pruritus -- an itch, or the sensation of an itch, according to the Cleveland Clinic 1. The sensation can range from a mild annoyance to severe discomfort that disrupts sleep and causes medical problems. While the function of nerves, chemicals and signals sent to the brain contribute to feelings of itchiness, the causes of itchy skin are many and sometimes unknown. The appearance of skin that itches helps with diagnosis.

Hives

Hives, also known as urticaria and welts, occur as itchy pink and red bumps that that appear on the body and fade within hours 2. New bumps appear and disappear and the condition can last for a few days or six weeks or more. Skinsight notes that nearly 90 percent of hive outbreaks are never tied to a cause or trigger. Health professionals believe hive outbreaks are a reaction of the immune system. Hives are triggered by allergies, medical conditions, stress, medications and infections.

Rash

Itchiness Behind the Ears

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A rash appears on the skin as an area of red and itchy skin that might be irritated, swollen or bumpy. The rash may appear as blisters or the skin might become scaly or crusty. Causes of rashes include medical conditions, allergies and substances such as poison ivy or chemicals that irritate the skin. Your genetic makeup or allergies can make you susceptible to rashes. Rashes are often caused by contact dermatitis, according to MedlinePlus 34. You might develop a rash very quickly or it might take days to appear. Scratching a rash usually interferes with healing. Treatment might include ointments or medications that relieve itching.

Dry Skin

Dry skin, also called xerosis, is a type of itchy skin, according to CNN Health. With dry skin, you do not see other skin changes and it appears that environmental factors are the cause of your dry skin. Extremes in weather, low humidity and extended use of central heating or air conditioning can cause dry skin. Your skin can become dry if you bath too often. You can treat and heal dry skin caused by environmental practices or personal habits by making changes and using products that alleviate itching and replace moisture in your skin.

Round, Itchy Patches

Dry Skin Patches in the Winter

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Fungal or tinea infections develop on the top layer of skin and appear as flat, round, itchy patches of skin, reports the "N.Y. Times Health" website 5. These infections include Athlete’s foot, ringworm and jock itch. Treatment usually involves medicated ointments.

Rough, Scaly Skin

Psoriasis, which is a skin disease, causes rough skin and scales that appear silver in color. Psoriasis is a chronic condition of the immune system that causes the build-up of dead skin cells on the skin, says MedlinePlus 34. The condition often causes the development of patches of red, dry, itchy skin that can become painful.