There are specific nerves that carry information about different bodily sensations (like an itch) to the brain. When these nerves are stimulated, they release various chemical messengers called cytokines that activate nearby nerves. Histamine is an example of a cytokine that is responsible for itching in allergic reactions. Once more and more nerves get stimulated, the messages bombard the brain, and the brain responds with directions to scratch. Itchiness, also known as pruritus, can be accompanied by and result in redness, bumps, and other kinds of rashes on the skin. In other cases, there are no changes in the skin. Itchiness can have a variety of causes that range from mild and temporary insect bites to specific skin conditions (e.g. eczema or psoriasis) to more serious medical conditions, such as liver and kidney disease. The main causes of itchy skin include:   Dry Skin - One of the most common causes of itchy skin is dry skin, which can be due to environmental factors (e.g., indoor heating or cooling, low humidity or too many baths or showers with drying cleaning agents) or inadequate amounts of water.  Skin Conditions - Eczema (atopic dermatitis) and psoriasis are common skin conditions typically accompanied by itching, reddened and irritated skin, bumps and blisters. Sunburns can be itchy as well.  Viral and Fungal Infections - Infections like chicken pox, measles, shingles, and genital and anal herpes can cause the body to feel very itchy.  Parasites - Pubic and head lice are itchy infestations by tiny wingless insects called lice.  Diseases - Liver disease is often accompanied by moderate to intense pruritus. Other conditions where itchy skin appears include certain blood disorders (e.g., iron deficiency anemia, polycythemia vera, etc.), cancer (such as leukemia and lymphoma), and thyroid disease.  Allergic reactions - Allergic reactions to insect bites, pollen, toxins from plants, cosmetics, personal products, and foods can cause mild to severe itching. Rashes caused by a contact dermatitis (a rash that results from skin contact with a substance or allergen) can be very itchy.  Adverse reactions to drugs - Skin reactions ranging from mild to severe itching are relatively common side effects of certain medications, including antibiotics, anti-fungal agents and some pain medications.  Nervous disorders - Conditions such as diabetes and multiple sclerosis affect the nerves and can result in an itchy sensation.  Pregnancy - Itchiness is often a “side effect” of pregnancy.  The itchy areas are usually on the abdomen, breasts, thighs and arms. It's important to determine whether you are simply suffering from dry skin or are experiencing another skin condition, like hives or a rash, that may be related to an allergic reaction or other medical condition. Dry skin is most common on your lower legs, stomach, arms, and thighs, and is characterized by scaling, itching and cracking of the skin. It is recommended that you consult your physician if you see any markings on the skin that may be indicative of something more serious than regular dry skin, including unexplainable or persistent rashes or hives.  Rashes are characterized by bumps on the skin, skin discoloration, scaling and blisters. Common rashes include poison ivy, heat rash, hives, and eczema. Non-infectious rashes can generally be treated with over-the-counter hydrocortisone creams, while oral antihistamines can help you relieve the itching. However, if you have a new and unexplainable rash, a fever or the rash lasts for more than a few days, you should seek your doctor.  Hives are characterized by slightly raised, pink or red swellings or dots on the skin that may be singular or connected in a group. Hives usually indicate an allergic reaction to certain foods, medicines, insect bites, pollen, and allergy shots. Other potential causes of hives include fungal and bacterial infections, stress, contact with chemicals, and exposure to sun, heat, cold, or water, among others. For most people, hives are not serious. If you suspect an allergic reaction is at work, your doctor can perform an allergy test and prescribe treatment (usually an antihistamine). If the itchiness is widespread, has no known cause and/or is not relieved within 2-3 days of trying the different remedies available above, make an appointment to see a physician to determine the cause of the itching and the best course of treatment for you.  If you have prolonged hives and/or rashes, talk to your doctor.  Medical diagnosis always depends on the underlying cause which can usually be determined by physical examination, a careful and complete medical history, and a variety of lab tests and imaging. In some cases, a small sample of skin may be taken in a biopsy so that the skin can be examined under a microscope. Most cases of skin itchiness are due at least in part to skin dryness and can be relieved even as the underlying cause takes time to be determined.
اعرف لماذا يحك الجلد. تعرف على سبب حكة الجلد. قيم أعراضك. استشر الطبيب.