A. Environmental Causes of Itchy Skin
1. Dry Skin
Dry skin (xerosis, winter itch) is common, especially in old people, and may be caused by cold weather, wind, sunburns, prolonged water exposure, frequent hot baths and using soaps (also washing powder and household cleansers) that can thin the protective oil layer on the skin and thus enable losing water through the skin.
Microbes from a normal skin flora break down the sweat (especially in the armpits and groin) and yield substances that cause itch. Excessive sweatingcan be observed in persons with primary hyperhidrosis (increased activity of sympathetic nerves, possibly caused by psychological reasons), or secondary hyperhidrosis (in elevated levels of thyroxine, in tuberculosis or malignancies).
3. Insect Bites
Insects (mosquitoes, flies, tics, bees, wasps, ants, spiders, scorpions) bites may cause a minor localized itchy and/or painful skin infection that usually heals on its own in several hours or few days. Some insect bites, especially bees may cause severe allergic reactions with generalized skin itch and swelling.
4. Infections and Infestations
- Fungi (e.g. Candida albicans) thrive well on the feet and in moist body folds (the groin, under the breasts). Dandruff (scalp skin shedding and itching) is also caused by fungi. Athlete’s foot.
- Parasitic skin infections: scabies, mites, lice, louse, cutaneus larva migrans, cercaria causing swimmers itch.
- Intestinal worms
- Bacterial infections, like infected acne are common in adolescents. Folliculitis caused by Staphylococcus aureus is common in athletes, impetigo is common in children. Hot tub folliculitis caused by Pseudomonas aeruginosa may arise after using non-properly treated pools or hot tubs. Read about other types of folliculitis.
- Viral skin infections
- infections of childhood: measles, rubella, chicken pox, infectious mononucleosis
- Herpes labialis usually appears close to the mouth, Herpes genitalis on the genital mucosa, and Herpes zoster (shingles) over the course of cranial nerves on the head or spinal nerves on the trunk.
- Viral hepatitis
- Hidradenitis suppurativa
5. Irritant Substances
Substances that may cause itching by irritating the skin (without causing skin inflammation):
- Fiberglass used as insulation material (glass wool) can cause skin and throat itching
- Detergents (washing powder) remove fat from the skin and thus dry it
Dermatitis is a non-infectious skin inflammation with red itchy rash, caused by touching, inhalation or ingestion of certain substances (4).
- Contact dermatitis can be allergic or non-allergic. Sharply delimited red itchy patches appear on the site of contact with wool clothes, necklesses, cosmetics, solvents…
- Photodermatitis is a result of effect of sunlight on certain chemicals, like medications or cosmetics, present in the skin.
- Generalized exfoliative dermatitis may be associated with use of antibiotics, barbiturates, or by psoriasis.
- Stasis dermatitis mostly occurs in patients with varicose veins on legs.
- Localized scratch dermatitis is a skin inflammation due to long term scratching.
- Benign mucosal pemphigoid – itchy blisters.
Allergic reaction to certain substance can occur in few minutes (early response), or 6-72 hours after (delayed response) contact with a triggering substance (allergen).
- Allergic reaction to foods or drugs commonly cause itchy/tingling sensations around the mouth and in the throat. Facial skin and lips may swell.
- Hay (pollen) allergies may cause difficulty breathing, runny nose, itchy skin and eyes.
- Allergic contact dermatitis is caused by Urushiol contained in poison ivy and poison oak.
- Atopic dermatitis appears mostly in children who also have asthma or hay fever.
- Other common allergies are hair dye allergies, allergies to lacquers, and the like.
- Hives (urticaria) is a type of allergic reaction with red raised itchy patches on the skin.
- Hyper-IgE Syndrome (itchy rash)
- Hyperimmunoglobulin E (IgE) syndrome
- Idiopathic hypereosinophilic syndrome
8. Adverse Effects of Medications and Therapy
- Medications causing itchy skin include: morphine, allopurinol, amiodarone, angiotensin-converting enzyme (ACE) inhibitors, estrogen, hydrochlorothizide, hydroxyethyl cellulose, opioids and simvastatin.
- Drug interactions causing itchy skin
- Blood transfusion and complications , plasma expanders.
- Graft-versus-host disease
9. Illegal Drugs and Itchy Skin
Cocaine, heroine, ecstasy and LSD abuse may all cause itch.
- Alcoholic intoxication
- Ciguatera poisoning, caused by ciguatoxin accumulated in some big tropical fish, may cause itch lasting from few hours to several months.
- Mercury poisoning can cause acrodynia – severe itching in infants in children
- Vitamin A toxicity
- Gold salts
- Nicotinic acid
- Fixed drug eruption
B. Diseases Causing Itch
1. Liver and Biliary Tract Diseases
Any liver or biliary tract disorder resulting in bile salts accumulation in the skin may cause itch. Diseases include hepatitis, cirrhosis, hepatic carcinoma, obstruction of the bile duct with gallstones, cancer and biliary atresia.
2. Gastrointestinal Diseases
- Intestinal parasites. Parasites or their eggs in the stool, and bloating may accompany itchines.
- Dumping syndrome
3. Kidney Failure
Any kidney disease that resulting in uraemia (increased urea level in blood), and accumulation of urate crystals in the skin may cause itch.
4. Skin Conditions
- Lichen planus
- In seborrheic dermatitis, yellow, greasy scales appear on the scalp, face and occasionally on other areas from unknown reason
- In nummular dermatitis, coin-shaped eczema appears on the various parts of the skin
- Perioral dermatitis mostly affects women between 20-60 years of age from unknown reason. Red rash appears around the mouth, nose and eyes.
5. Nutrient Deficiencies
- Iron and vitamin A deficiency may cause itchy skin.
6. Hormonal Disorders
- Hyper/hypo-thyroidism, hyper/hypo-parathyroidism
- Later months of pregnancy (usually does not indicate any abnormality)
- Menopause (perimenopausal pruritus)
7. Autoimmune Diseases
- Sjögren’s syndrome
- Systemic sclerosis
- Rheumatoid arthritis (and other types of arthritis)
- Hashimoto’s thyroiditis
- Vasculitis (several types)
- Acinic cell carcinoma (most often found in the pancreas, salivary glands, palate and upper lip)
- Hodgkin’s lymphoma
- Non-Hodgkin’s lymphoma
- Polycythemia vera
- Carcinoid syndrome
- Paraneoplastic syndrome
- Acanthosis nigricans are dry bumpy discolored skin lesions that often appear in abdominal malignancies.
- Melanoma and most of other skin malignancies may itch.
- Cancer of cervix, prostate or colon.
9. Central Nervous System Disorders
- Brain abscess, tumor or other disorders
- Epidural anesthesia (when opioids are administered into the lumbar part of the spinal canal to provide anesthesia of abdomen, back, buttocks and legs).
Causes of Non-Itchy Rash
The rashes in below listed disorders are usually not itchy.
- Acne (may occasionally itch)
- Actinic (solar) keratosis (may occasionally itch)
- Alcohol-induced pseudo-Cushing syndrome – abdominal stretch marks (rare)
- Bejel (a form of non-sexually transmitted syphilis) : non-itchy mouth and skin sores, caused by a bacterium Treponema, transmitted via utensils, mainly among children in the Middle East and Africa
- Campbell-De Morgan spots are small, red, raised, cherry angiomas, few mm in diameter, appearing on arms, neck, upper chest and back; they are common, harmless, and easy to remove with a laser
- Hemangioma – Port-wine stain
- Infectious mononucleosis
- Juvenile rheumatoid arthritis
- Keratosis pilaris – goose bumps (rarely may itch)
- Lactate dehydrogenase deficiency is a genetic disease with an exercise intolerance
- Roseola is a viral disease appearing in small children
- Salmon patch is a pink discoloration, commonly appearing in infants on the nape of the neck or forehead, spontaneously disappearing until the end of the first year of life
- Scars (may occasionally itch)
- Skin tags – soft harmless lesions that hang off the skin
- Rocky Mountain spotted fever
- Systemic lupus erythematosus (SLE)
- Warts (rarely may itch)