Editing Itch (section)

== Causes ==
[[File:Scabies-burrow.jpg|thumb|[[Scabies]] is one cause of itching]]
[[File:CercariaDermatitis.JPG|thumb|[[Swimmer's itch]]]]
[[File:Tinea pedis interdigitalis.jpg|thumb|[[Athlete's foot]] (showing the toes from below plus the front part of the sole)]]

=== Infectious ===
*[[Body louse]], found in substandard living conditions
*[[Cutaneous larva migrans]], a skin disease caused by [[hookworm]] infection
*[[Head lice]], if limited to the neck and scalp
*[[Herpes]], a viral disease
*[[Insect bite]]s, such as those from [[mosquitos]] or [[chiggers]]
*[[Pubic lice]], if limited to the [[genital area]]
*[[Scabies]], especially when several other persons in close contact also itch
*[[Shaving#Razor burn|Shaving]], which may irritate the skin
*[[Swimmer's itch]], a short-term immune reaction
*[[Chickenpox|Varicella]]&nbsp;– i.e. chickenpox, prevalent among young children and highly contagious
*[[Tungiasis]], ectoparasite of skin

=== Environmental and allergic ===
*[[Allergic reaction]] to contact with specific chemicals, such as [[urushiol]], derived from [[poison ivy]] or [[poison oak]], or [[Balsam of Peru]], found in many foods and fragrances.<ref>{{cite journal |vauthors=Pfützner W, Thomas P, Niedermeier A, Pfeiffer C, Sander C, Przybilla B |display-authors=3 |title=Systemic contact dermatitis elicited by oral intake of Balsam of Peru |journal=Acta Dermato-Venereologica |volume=83 |issue=4 |pages=294–295 |date=2003-02-20 |pmid=12926805 |doi=10.1080/00015550310016599 |doi-access=free}}</ref><ref>{{cite journal |vauthors=Usatine RP, Riojas M |title=Diagnosis and management of contact dermatitis |journal=American Family Physician |volume=82 |issue=3 |pages=249–255 |date=August 2010 |pmid=20672788 |url=http://www.aafp.org/afp/2010/0801/p249.html |access-date=2014-04-09 |publisher=Aafp.org |archive-date=2014-04-09 |archive-url=https://web.archive.org/web/20140409161328/http://www.aafp.org/afp/2010/0801/p249.html |url-status=live }}</ref> Certain allergens may be diagnosed in a [[patch test]].<ref>{{cite book |url=https://books.google.com/books?id=QhWgKgiT6FoC&pg=PA329 |title=Metalworking Fluids |edition=Second |publisher=CRC Press |isbn=142001773X |date=2006 |vauthors=Byers JP |access-date=2016-03-05 |archive-date=2023-01-12 |archive-url=https://web.archive.org/web/20230112213927/https://books.google.com/books?id=QhWgKgiT6FoC&pg=PA329 |url-status=live }}</ref><ref>{{cite book |url=https://books.google.com/books?id=Me5rAAAAMAAJ&q=pruritus+%22patch+test%22 |title=Introduction to clinical allergy |vauthors=Feingold BF |veditors=Byers JP |publisher=the University of Michigan |date=1973 |isbn=0398027978 |access-date=2020-06-24 |archive-date=2023-01-12 |archive-url=https://web.archive.org/web/20230112223856/https://books.google.com/books?id=Me5rAAAAMAAJ&q=pruritus+%22patch+test%22 |url-status=live }}</ref>
*[[Foreign body|Foreign object]]s on the skin are the most common cause of non-pathological itching. 
*[[Photodermatitis]]&nbsp;– [[sunlight]] reacts with chemicals in the skin, leading to the formation of irritant metabolites.
*[[Urticaria]] (also called [[hives]]) usually causes itching.

=== Dermatologic ===
* [[Dandruff]], an unusually large amount of flaking is associated with this sensation.
* [[Punctate palmoplantar keratoderma]], a group of disorders characterized by abnormal thickening of the palms and soles.
* [[Skin condition]]s (such as [[psoriasis]], [[eczema]], [[seborrhoeic dermatitis]], [[sunburn]], [[athlete's foot]], and [[hidradenitis suppurativa]]). Most are of an inflammatory nature.
* [[Wound healing|Scab]] healing, [[scar]] growth, and the development or emergence of [[Melanocytic nevus|moles]], [[pimple]]s, and [[ingrown hair]]s from below the epidermis.
* [[Xerosis]], dry skin, 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.

=== Other diseases ===
* [[Diabetes mellitus]], a group of metabolic diseases in which a person has high blood sugar
* [[Hyperparathyroidism]], overactivity of the parathyroid glands resulting in excess production of parathyroid hormone (PTH)<ref>LaBagnara, James. [http://www.emedicine.com/ent/TOPIC299.HTM eMedicine&nbsp;–Hyperparathyroidism] {{Webarchive|url=https://web.archive.org/web/20081202153050/http://www.emedicine.com/ent/topic299.htm |date=2008-12-02 }}. emedicine.com</ref>
* [[Iron deficiency anemia]], a common anemia (low red blood cell or hemoglobin levels)
* [[Cholestasis]], where bile acids leaking into the serum activate peripheral opioid receptors, resulting in the characteristic generalized, severe itching
* [[Malignancy]] or internal cancer, such as [[lymphoma]] or [[Hodgkin's disease]]<ref>{{Cite journal |last1=Jovičić |first1=Sanja |last2=Balaban |first2=Jagoda |last3=Gajanin |first3=Vesna |date=2023-06-24 |title=Association of systemic diseases with chronic pruritus |journal=Scripta Medica |volume=54 |issue=2 |pages=163–167 |doi=10.5937/scriptamed54-43882 |issn=2490-3329|doi-access=free }}</ref>
* [[Polycythemia]], which can cause generalized itching due to increased histamines
* [[Psychiatric]] disease ("[[psychogenic disease|psychogenic itch]]", as may be seen in [[delusional parasitosis]])
* [[Thyroid]] illness
* [[Uraemia]]&nbsp;– the itching sensation this causes is known as [[uremic pruritus]]

=== Medication ===
* Drugs (such as [[opioids]]) that activate histamine (H1) receptors or trigger histamine release
* [[Chloroquine]], a drug used in the treatment and prevention of [[malaria]]
* [[Bile acid]] congeners such as obeticholic acid

=== Related to pregnancy ===
* [[Gestational pemphigoid]], a dermatosis of pregnancy
* [[Intrahepatic cholestasis of pregnancy]], a medical condition in which cholestasis occurs
* [[Pruritic urticarial papules and plaques of pregnancy]] (PUPPP), a chronic hives-like rash

=== Other ===
* [[Menopause]], or changes in hormonal balances associated with aging
*[[Terminal illness]]<ref name=":1">{{Cite journal |last1=Boehlke |first1=Christopher |last2=Joos |first2=Lisa |last3=Coune |first3=Bettina |last4=Becker |first4=Carola |last5=Meerpohl |first5=Joerg J. |last6=Buroh |first6=Sabine |last7=Hercz |first7=Daniel |last8=Schwarzer |first8=Guido |last9=Becker |first9=Gerhild |date=2023-04-14 |title=Pharmacological interventions for pruritus in adult palliative care patients |url=https://pubmed.ncbi.nlm.nih.gov/37314034 |journal=The Cochrane Database of Systematic Reviews |volume=4 |issue=2023 |pages=CD008320 |doi=10.1002/14651858.CD008320.pub4 |issn=1469-493X |pmid=37314034 |pmc=11339634 |pmc-embargo-date=August 22, 2025 |access-date=2023-07-27 |archive-date=2023-07-27 |archive-url=https://web.archive.org/web/20230727181335/https://pubmed.ncbi.nlm.nih.gov/37314034/ |url-status=live }}</ref>