NationMaster - Encyclopedia: Contact dermatitis

Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants. Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight. Image File history File links Information_icon. ... Shortcut: WP:WIN Wikipedia is an online encyclopedia and, as a means to that end, also an online community. ... Shortcut: WP:CU Marking articles for cleanup This page is undergoing a transition to an easier-to-maintain format. ... This Manual of Style has the simple purpose of making things easy to read by following a consistent format — it is a style guide. ... Image File history File links Circle-question-red. ... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following codes are used with International Statistical Classification of Diseases and Related Health Problems. ... // L00-L99 - Diseases of the skin and subcutaneous tissue (L00-L08) Infections of the skin and subcutaneous tissue (L00) Staphylococcal scalded skin syndrome (L01) Impetigo (L02) Cutaneous abscess, furuncle and carbuncle (L03) Cellulitis (L04) Acute lymphadenitis (L05) Pilonidal cyst (L08) Other local infections of skin and subcutaneous tissue (L081) Erythrasma... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... The Disease Bold textDatabase is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... eMedicine is an online clinical medical knowledge base that was founded in 1996. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... It has been suggested that this article or section be merged with Epidermis (skin). ... An allergen is any substance (antigen), most often eaten or inhaled, that is recognized by the immune system and causes an allergic reaction. ... The word irritant may refer to: Look up Irritant in Wiktionary, the free dictionary. ... A phototoxic substance is a chemical compound which becomes toxic only when exposed to light. ...

Description

Only the superficial regions of the skin are affected in contact dermatitis. Inflammation of the affected tissue is present in the epidermis (the outermost layer of skin) and the outer dermis (the layer beneath the epidermis) (ESCD 2006)^[1]. Unlike contact urticaria in which a rash appears within minutes of exposure and fades away within minutes to hours, contact dermatitis takes days to fade away and then only if the skin no longer comes in contact with the allergen or irritant.^[2] Chronic contact dermatitis can develop where the removal of the offending agent no longer provides expected relief. In North America, the most common allergic contact dermatitis is caused by poison ivy. Contact dermatitis results in large, burning, and itchy rashes, and these can take anywhere from several days to weeks to heal. Common causes of irritant contact dermatitis are harsh (highly alkaline) soaps, detergents, and cleaning products.^[3] Look up Epidermis in Wiktionary, the free dictionary. ... The dermis is a layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. ... Urticaria or hives is a relatively common form of allergic reaction that causes raised red skin welts. ... Binomial name Toxicodendron radicans (L.) Kuntze Poison-ivy (Toxicodendron radicans or Rhus toxicodendron), in the family Anacardiaceae, is a woody vine that is well-known for its ability to produce urushiol, a skin irritant which for most people will cause an agonizing, itching rash. ...

Types of contact dermatitis

There are three types of contact dermatitis: irritant contact, allergic contact, and photocontact dermatitis. Photocontact dermatitis is divided into two catergories: phototoxic and photoallergic.

Irritant Contact Dermatitis (ICD)

This is the most common form of contact dermatitis, affecting around 1-2% of healthy Europeans (ESCD 2006), and can be caused by either an acute or chronic exposure to a toxic insult. It is also referred to as non-allergic contact dermatitis (along with traumiterative or housewives' eczema) referring to its non-immunological mechanism of toxicity. It is caused by either chemical or physical irritants. People who do a lot of wetwork (mothers of small children, hairdressers, nurses, chefs) are very prone to developing ICD.

Chemical Irritant Contact Dermatitis (CICD) can be subdivided into acute and chronic ICD which is usually associated with strong and weak irritants respectively (HSE MS24)^[4]. The following definition is provided by Mathias and Maibach (1978):^[5] a nonimmunologic local inflammatory reaction characterized by erythema, edema, or corrosion following single or repeated application of a chemical substance to an identical cutaneous site. The mechanism of action varies between toxins. Detergents, surfactants, extremes of pH and organic solvents all have the common effect of directly affecting the barrier properties of the epidermis. These include removing fat emulsion, inflicting cellular damage on the epithelium, or increasing the transepidermal water loss by damaging the horny layer water-binding mechanisms and damaging the DNA which causes the layer to thin. As suggested previously, strong concentrations of irritants cause an acute effect, but this is not as common as the accumulative, chronic effect of weaker irritants whose deleterious effects build up with subsequent doses (ESCD 2006). Wikipedia does not yet have an article with this exact name. ... This article or section does not cite its references or sources. ...

Common chemical irritants implicated: solvents (alcohol, xylene, turpentine, esters, acetone, ketones and others); metalworking fluids (neat oils, water-based matalworking fluids with surfactants); rubber (gloves); kerosene; ethylene oxide; surfactants in topical medications and cosmetics (sodium lauryl sulfate); alkalis (drain cleaners, strong soap with lye residues).

Physical irritant contact dermatitis (PICD) is a less well researched form of ICD (Maurice-Jones et al)^[6]. This is due to its highly varied and numerous mechanisms of action as well as a lack of a test for its diagnosis. A complete patient history combinated with negative allergic patch testing is usually necessary to reach a correct diagnosis. The simplest form of PICD results from prolonged rubbing, although the diversity of implicated irritants is far wider.^{[citation needed]} Examples include paper friction, fiberglass, and scratchy clothing. A patch test is a method used to determine if a specific substance causes inflammation of the skin. ...

Many plants cause ICD by directly irritating the skin. Some plants act through their spines or irritant hairs. Some plant such as the buttercup, spurge and daisy, act by chemical means. The sap of these plants contains a number of alkaloids, glycosides, saponins, anthroquinones, and in the case of plant bulbs, irritant calcium oxalate crystals, all of which can cause CICD (Mantle and Lennard, 2001)^[7].

Allergic Contact Dermatitis (ACD)

This condition is the manifestation of an allergic response caused by contact with a substance. A list of common allergens is shown in Table 1 (Kucenic and Belsito, 2002)^[8]. Although less common than ICD, it is accepted to be the most prevalent form of immunotoxicity found in humans (Kimble et al 2002)^[9]. By its allergic nature, this form is a hypersensitive reaction which is atypical within the population. The mechanisms by which these reactions occur are complex, with many levels of fine control. Their immunology centres around the interaction of immunoregulatory cytokines and discrete subpopulations of T lymphocytes.

ACD arises as a result of two essential stages - an induction phase which primes and sensitises the immune system for an allergic response, and an elicitation phase in which this response is triggered (Kimble et al 2002). As such, ACD is termed a Type IV delayed hypersensitivity reaction involving a cell-mediated allergic response. Contact allergens are essentially soluble haptens (low in molecular weight) and, as such, have the physico-chemical properties that allow them to cross the stratum corneum of the skin. They can only cause their response as part of a complete antigen, involving their association with epidermal proteins forming hapten-protein conjugates. This in turn requires them to be protein-reactive.

The conjugate formed is then recognised as a foreign body by the Langerhans Cells (LC) (and in some cases Dentritic Cells (DC)), which then internalise the protein, transport it via the lymphatic system to the regional lymph nodes and present the antigen to T-lymphocytes. As mentioned earlier, this process is controlled by cytokines and chemokines, with tumour necrosis factor alpha (TNF-α) and certain members of the interleukin family (1, 13 and 18) and their action serves either to promote or to inhibit the mobilisation and migration of these LCs. (Kimble et al 2002) As the Langerhans cells are transported to the lymph nodes, they become differentiated and transform into Dentric Cells which are immunostimulatory in nature.

Once within the lymph glands, the differentiated DCs act to present the allergenic epitope associated with the allergen to T lymphocytes. As a result, these T cells divide and differentiate, clonally multiplying so that if the allergen is experienced again by the individual, these T cells will respond more quickly and more aggressively.

As mentioned briefly, the immunological reaction involved in ACD is highly complex with many levels of fine control. Kimbe et al (2002) explore these complexities in short. It appears that there are two major phenotypes of cytokine production (although there exists a gradient of subsets in between), and these are termed T-helper 1 and 2 (Th1 and Th2). Although these cells initially differentiate from a common stem cell, they develop with time as the immune system matures. Th1 phenotypes are characterised by their focus on Interleukin and Interferon, while Th2 cells action is centred more around the regulation of IgE by cytokines. The CD4 and CD8 T lymphocyte subsets also have been found to contribute to differential cytokine regulation, with CD4 having been shown to produce high levels of IL-4 and IL10 while solely CD8 cells are associated with low levels of IFN?. These two cell subtypes are also closely associated with the cell matrix interactions essential for the pathogenesis of ACD.

It has been suggested (White et al 1986) ^[10] that there appears to be a threshold to the mechanisms of allergic sensitisation by ACD-associated allergens. This is thought to be linked to the level at which the toxin induces the up-regulation of the required mandatory cytokines and chemokines. It has also been proposed that the vehicle in which the allergen reaches the skin could take some responsibility in the sensitisation of the epidermis by both assisting the percutaneous penetration and causing some form of trauma and mobilisation of cytokines itself.

For discussion on alleged health effects of thiomersal in vaccines, see Thiomersal controversy. ... Neomycin is an aminoglycoside antibiotic that is found in many topical medications such as creams, ointments and eyedrops. ...

Photocontact Dermatitis (PCD)

Sometimes termed "photoaggravated"(Bourke et al 2001)^[13], and divided into two categories, phototoxic and photoallergic, PCD is the eczematous condition which is triggered by an interaction between an otherwise unharmful or less harmful substance on the skin and ultraviolet light (320-400nm UVA) (ESCD 2006), therefore manifesting itself only in regions where the sufferer has been exposed to such rays. Without the presence of these rays, the photosensitiser is not harmful. For this reason, this form of contact dermatitis is usually associated only with areas of skin which are left uncovered by clothing. The mechanism of action varies from toxin to toxin, but is usually due to the production of a photoproduct. Toxins which are associated with PCD include the psoralens. Psoralens are in fact used therapeutically for the treatment of psoriasis, eczema and vitiligo.

Photocontact dermatitis is another condition where the distinction between forms of contact dermatitis is not clear cut. Immunological mechanisms can also play a part, causing a response similar to ACD.

Prevention

Since contact dermatitis relies on an irritant or an allergen to initiate the reaction, it is important for the patient to identify the responsible agent and avoid it. This can be accomplished by having patch tests, a method commonly known as allergy testing. The patient must know where the irritant or allergen is found to be able to avoid it. It is important to also note that chemicals sometimes have several different names. This doesn't always have a great success rate. ^[14]

Summary

The distinction between the various types of contact dermatitis is based on a number of factors. The morphology of the tissues, the histology, and immunologic findings are all used in diagnosis of the form of the condition. However, as suggested previously, there is some confusion in the distinction of the different forms of contact dermatitis (Reitschel 1997)^[15]. Using histology on its own is insufficient, as these findings have been acknowledged not to distinguish (Rietschel, 1997), and even positive patch testing does not rule out the existence of an irritant form of dermatitis as well as an immunological one. It is important to remember, therefore, that the distinction between the types of contact dermatitis is often blurred, with, for example, certain immunological mechanisms also being involved in a case of irritant contact dermatitis.

References

^ ESDC. What is contact dermatitis. European Society of Contact Dermatitis, http://orgs.dermis.net
^ DermNet NZ: Contact Dermatitis. Retrieved on August 14, 2006.
^ Irritant Contact Dermatitis, at DermNetNZ, http://www.dermnetnz.org/dermatitis/contact-irritant.html
^ HSE Guidance Notes. Guidance Note MS 24 - Health Surveillance of occupational skin disease. http://www.hse.gov.uk/pubns/ms24.pdf
^ Mathias CG, Maibach HI. Dermatotoxicology monographs I. Cutaneous irritation: factors influencing the response to irritants. Clin Toxicol. 1978;13(3):333-46. Review. No abstract available.
^ Morris-Jones R, Robertson SJ, Ross JS, White IR, McFadden JP, Rycroft RJ. Dermatitis caused by physical irritants. Br J Dermatol. 2002 Aug;147(2):270- 5. Review.
^ Mantle D, Lennard TWJ. Plants and the skin. Brit J Derm Nurs. 2001 (Summer).
^ Kucenic MJ, Belsito DV.Occupational allergic contact dermatitis is more prevalent than irritant contact dermatitis: a 5-year study. J Am Acad Dermatol. 2002 May;46(5):695-9.
^ Kimble I, Basketter DA, Gerberick GF, Dearman RJ. Allergic contact dermatitis. Int Immunopharmacol. 2002 Feb;2(2-3):201-11. Review.
^ White SI, Friedmann PS, Moss C, Simpson JM.The effect of altering area of application and dose per unit area on sensitization by DNCB. Br J Dermatol. 1986 Dec;115(6):663-8.
^ Allergy to fragrance mix at DermNetNZ, http://dermnetnz.org/dermatitis/fragrance-allergy.html
^ Mayo Clinic study, http://http://www.mayoclinic.org/news2006-rst/3268.html
^ Bourke J, Coulson I, English J; British Association of Dermatologists. Guidelines for care of contact dermatitis. Br J Dermatol. 2001 Dec;145(6):877-85.
^ DermNet NZ: Contact Dermatitis. Retrieved on August 18, 2006.
^ Rietschel RL. Mechanisms in irritant contact dermatitis. Clin Dermatol. 1997 Jul-Aug;15(4):557-9.

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