Allergic contact dermatitis
Encyclopedia
Allergic contact dermatitis is a form of contact dermatitis
that is the manifestation of an allergic response caused by contact with a substance.
Although less common than ICD, ACD is accepted to be the most prevalent form of immunotoxicity found in humans. By its allergic nature, this form of contact dermatitis is a hypersensitive
reaction that 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.
, involving their association with epidermal proteins forming hapten-protein conjugates. This, in turn, requires them to be protein-reactive.
The conjugate formed is then recognized as a foreign body by the Langerhans cell
s (LCs) (and in some cases other Dendritic cell
s (DCs)), which then internalize the protein; transport it via the lymphatic system
to the regional lymph nodes; and present the antigen to T-lymphocytes. This process is controlled by cytokines and chemokines - with tumor 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 mobilization and migration of these LCs. (Kimble et al. 2002) As the LCs are transported to the lymph nodes, they become differentiated and transform into DCs, which are immunostimulatory in nature.
Once within the lymph glands, the differentiated DCs present the allergenic epitope associated with the allergen to T lymphocytes. These T cells then 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.
White et al. have suggested that there appears to be a threshold to the mechanisms of allergic sensitisation by ACD-associated allergens (1986). 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 mobilization of cytokines itself.
causing it, the rash can ooze, drain or crust and it can become raw, scaled or thickened. Also, it is possible that the skin lesion does not take the form of a rash but it may include papules, blisters, vesicles or even a simple red area. The main difference between the rash caused by allergic contact dermatitis and the one caused by irritant contact dermatitis is that the first one tends to be confined to the area where the trigger touched the skin, whereas in the second case, the rash is more likely to be more widespread on the skin. Another characteristic of the allergic contact dermatitis rash is that it usually appears after a day or two after exposure to the allergen, unlike irritant contact dermatitis that appears immediately after the contact with the trigger.
Other symptoms may include itching, skin redness or inflammation
, localized swelling and the area may become more tender or warmer. If left untreated, the skin may darken and become leathery and cracked. Pain can also be present.
The symptoms of allergic contact may persist for as long as one month before resolving completely. Once an individual has developed a skin reaction to a certain substance it is most likely that he will have it for the rest of the life, and the symptoms will reappear when in contact with the allergen.
The first step in treating the condition is applying a damp cloth shortly after the skin problem first shows to make sure that all of the irritant has been removed from the area. In some cases, the best treatment is to do nothing to the area.
In mild to moderate cases, patients may use skin creams containing corticosteroids to reduce the inflammation. These creams should be used carefully and according to the instructions they come with because when overused over longer periods of time they can cause serious skin conditions. Also, calamine lotion and cool oatmeal
baths may relieve itching.. Over the counter diphenhydramine by mouth is helpful for night time itching.
Usually, severe cases are treated with systemic corticosteroids which may be tapered gradually, with various dosing schedules ranging from a total of 12 - 20 days to prevent the recurrence of the rash as well as a topical corticosteroid. Tacrolimus ointment or pimecrolimus cream can also be used additionally to the corticosteroid creams or instead of these. Oral antihistamines such as diphenhydramine or hydroxyzine may also be used in more severe cases to relieve the intense itching. Topical antihistamines are not advised as there might be a second skin reactions from the lotion itself.
The other symptoms caused by allergic contact dermatitis are generally eased with wet dressings and drying lotions to stop the itching. In most cases however, medication or actual treatment is not required as long as the trigger has been identified and avoided. The discomfort caused by the symptoms may be relieved by wearing smooth-textured clothing to avoid more skin irritation or by avoiding soaps with perfumes and dyes.
Commonly, the symptoms may resolve without treatment in 2 to 4 weeks but specific medication may hasten the healing as long as the trigger is avoided. Also, the condition might become chronic if the allergen is not detected and therefore it is not avoided.
. In some cases doctors can establish an accurate diagnosis based on the symptoms that the patient experiences and on the rash's appearance. In the case of a single episode of allergic contact dermatitis, this is all that is necessary. Chronic and/or intermittent rashes which are not readily explained by history and physical exam often will benefit from further testing. A patch test (contact delayed hypersensitivity allergy test) is a commonly used examination to determine the exact cause of an allergic contact dermatitis. According to the American Academy of Allergy, Asthma, and Immunology, "patch testing is the gold standard for contact allergen identification".
The patch test consists in applying small quantities of potential allergens to small patches and which are then placed on the skin. After two days, they are removed and if a skin reaction occurred to one of the substances applied, a raised bump will be noticeable underneath the patch. The tests are again read at 72 or 96 hours after application.
Patch testing is used for patients who have chronic, recurring contact dermatitis. Other tests that may be used to diagnose contact dermatitis and rule out other potential causes of the symptoms include a skin biopsy and culture of the skin lesion.
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....
that is the manifestation of an allergic response caused by contact with a substance.
Although less common than ICD, ACD is accepted to be the most prevalent form of immunotoxicity found in humans. By its allergic nature, this form of contact dermatitis is a hypersensitive
Hypersensitivity
Hypersensitivity refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. These reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized state of the host. The four-group classification...
reaction that 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.
Pathophysiology
ACD arises as a result of two essential stages: an induction phase, which primes and sensitizes 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 antigenAntigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
, involving their association with epidermal proteins forming hapten-protein conjugates. This, in turn, requires them to be protein-reactive.
The conjugate formed is then recognized as a foreign body by the Langerhans cell
Langerhans cell
Langerhans cells are dendritic cells of the skin and mucosa, and contain large granules called Birbeck granules. They are present in all layers of the epidermis, but are most prominant in the stratum spinosum. They also occur in the papillary dermis, particularly around blood vessels, as well as...
s (LCs) (and in some cases other Dendritic cell
Dendritic cell
Dendritic cells are immune cells forming part of the mammalian immune system. Their main function is to process antigen material and present it on the surface to other cells of the immune system. That is, dendritic cells function as antigen-presenting cells...
s (DCs)), which then internalize the protein; transport it via the lymphatic system
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
to the regional lymph nodes; and present the antigen to T-lymphocytes. This process is controlled by cytokines and chemokines - with tumor 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 mobilization and migration of these LCs. (Kimble et al. 2002) As the LCs are transported to the lymph nodes, they become differentiated and transform into DCs, which are immunostimulatory in nature.
Once within the lymph glands, the differentiated DCs present the allergenic epitope associated with the allergen to T lymphocytes. These T cells then 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.
White et al. have suggested that there appears to be a threshold to the mechanisms of allergic sensitisation by ACD-associated allergens (1986). 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 mobilization of cytokines itself.
Allergens
Common allergens implicated include the following:- NickelNickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
(nickel sulfate hexahydrate) - metal frequently encountered in jewelry and clasps or buttons on clothing - GoldGoldGold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
(gold sodium thiosulfate) - precious metal often found in jewelry and dental materials - Balsam of Peru (MyroxylonMyroxylonMyroxylon J.R.Forst. & G.Forst is a synonym of Xylosma.Myroxylon is a genus of two species of Central American and South American trees in the Fabaceae . The tree is well known in the western world as the source for Peru balsam and Tolu balsam. The tree is often called Quina or Balsamo...
pereirae) - a fragrance used in perfumes and skin lotions, derived from tree resin (see also Tolu balsamTolu balsamTolu balsam or balsam of Tolu is the resinous secretion of Myroxylon balsamum.The resin is still used in certain cough syrup formulas. However its main use in the modern era is in perfumery, where it is valued for its warm, mellow yet somewhat spicy scent. It is also used as a natural remedy for...
). It may also be a component of artificial vanilla and/or cinnamon flavorings. - ChromiumChromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
- used in the tanning of leather. Also a component of uncured cement/mortar, facial cosmetics and some bar soaps. - Oily coating from plants of the ToxicodendronToxicodendronToxicodendron a genus of flowering plants in the sumac family, Anacardiaceae. It contains woody trees, shrubs and vines, including poison ivy, poison oak, and the lacquer tree. All members of the genus produce the skin-irritating oil urushiol, which can cause a severe allergic reaction...
genus: poison ivyPoison ivyToxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it...
, poison oakWestern Poison-oakToxicodendron diversilobum, western poison oak or Pacific poison-oak is in the Anacardiaceae family and is a plant best known for its ability to cause allergic rashes after contact...
, and poison sumacPoison SumacPoison sumac is a woody shrub or small tree growing to 7 m tall. All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans...
. - ThimerosalThiomersalThiomersal , and commonly known in the US as thimerosal, is an organomercury compound. This compound is a well established antiseptic and antifungal agent....
- a mercury compound used in local antiseptics and in vaccines - NeomycinNeomycinNeomycin is an aminoglycoside antibiotic that is found in many topical medications such as creams, ointments, and eyedrops. The discovery of Neomycin dates back to 1949. It was discovered in the lab of Selman Waksman, who was later awarded the Nobel Prize in Physiology and medicine in 1951...
- a topical antibiotic common in first aid creams and ointments, cosmetics, deodorant, soap and pet food. Found by itself, or in Polysporin or Triple Antibiotic - Fragrance mix - a group of the eight most common fragrance allergens found in foods, cosmetic products, insecticides, antiseptics, soaps, perfumes and dental products
- FormaldehydeFormaldehydeFormaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
- a preservative with multiple uses, e.g., in paper products, paints, medications, household cleaners, cosmetic products and fabric finishes. Often released into products by the use of formaldehyde releasers such as imidazolidinyl urea, diazolidinyl ureaDiazolidinyl ureaDiazolidinyl urea is an antimicrobial preservative used in cosmetics. It is chemically related to imidazolidinyl urea which is used in the same way. Diazolidinyl urea acts as a formaldehyde releaser....
, Quaternium-15Quaternium-15Quaternium-15 is a quaternary ammonium salt used as a preservative in many cosmetics and industrial substances. It acts as a formaldehyde releaser...
, DMDM Hydantoin and 2-bromo-2-nitropropane-1,3-diol. - CobaltCobaltCobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
chloride - metal found in medical products; hair dye; antiperspirant; metal-plated objects such as snaps, buttons or tools; and in cobalt blue pigment - BacitracinBacitracinBacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, isolation of which was first reported in 1945....
- a topical antibiotic found by itself, or as Polysporin or Triple Antibiotic - Quaternium-15Quaternium-15Quaternium-15 is a quaternary ammonium salt used as a preservative in many cosmetics and industrial substances. It acts as a formaldehyde releaser...
- preservative in cosmetic products (self-tanners, shampoo, nail polish, sunscreen) and in industrial products (polishes, paints and waxes). - Colophony (Rosin) - Rosin, sap or sawdust typically from spruce or fir trees
- Topical steroidTopical steroidTopical steroids are the topical forms of corticosteroids. Topical steroids are the most commonly prescribed topical medications for the treatment of rash, eczema, and dermatitis. Topical steroids have anti-inflammatory properties, and are classified based on their vasoconstriction abilities. There...
- see steroid allergy - Photographic developerPhotographic developerIn the processing of photographic films, plates or papers, the photographic developer is a chemical that makes the latent image on the film or print visible. It does this by reducing the silver halides that have been exposed to light to elemental silver in the gelatine matrix...
s, especially those containing metolMetolMetol is the chemical compound with the name monomethyl-p-aminophenol hemisulfate. It is a developing agent used in black & white photographic developers... - Topical anestheticTopical anestheticA topical anesthetic is a local anesthetic that is used to numb the surface of a body part. They can be used to numb any area of the skin as well as the front of the eyeball, the inside of the nose, ear or throat, the anus and the genital area. Topical anesthetics are available in creams,...
s such as pramoxine or diphenhydramineDiphenhydramineDiphenhydramine hydrochloride is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties which is mainly used to treat allergies. Like most other first-generation antihistamines, the drug also has a powerful hypnotic effect, and for this reason...
, after prolonged use - MethylchloroisothiazolinoneMethylchloroisothiazolinoneMethylchloroisothiazolinone is a preservative with antibacterial and antifungal effects within the group of isothiazolinones. It is effective against gram-positive and gram-negative bacteria, yeast, and fungi....
/MethylisothiazolinoneMethylisothiazolinoneMethylisothiazolinone or MIT, sometimes erroneously called methylisothiazoline, is a powerful biocide and preservative within the group of isothiazolinones, used amongst others in shampoos and body care products.-Applications:...
is a preservative used in wash-off products such as shampoos/conditioners.
Symptoms
The symptoms of allergic contact dermatitis are very similar to the ones caused by irritant contact dermatitis, which makes the first even harder to diagnose. The first sign of allergic contact dermatitis is the presence of the rash or skin lesion at the site of exposure. Depending on the type of allergenAllergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
causing it, the rash can ooze, drain or crust and it can become raw, scaled or thickened. Also, it is possible that the skin lesion does not take the form of a rash but it may include papules, blisters, vesicles or even a simple red area. The main difference between the rash caused by allergic contact dermatitis and the one caused by irritant contact dermatitis is that the first one tends to be confined to the area where the trigger touched the skin, whereas in the second case, the rash is more likely to be more widespread on the skin. Another characteristic of the allergic contact dermatitis rash is that it usually appears after a day or two after exposure to the allergen, unlike irritant contact dermatitis that appears immediately after the contact with the trigger.
Other symptoms may include itching, skin redness or inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
, localized swelling and the area may become more tender or warmer. If left untreated, the skin may darken and become leathery and cracked. Pain can also be present.
The symptoms of allergic contact may persist for as long as one month before resolving completely. Once an individual has developed a skin reaction to a certain substance it is most likely that he will have it for the rest of the life, and the symptoms will reappear when in contact with the allergen.
Treatment
The main treatment to cure allergic contact dermatitis consists of avoiding the allergen. Persons who develop the rash and the other symptoms from a certain trigger are most likely to have it for the rest of their lives and detecting and avoiding the allergen is mandatory in treating the condition and resolving its symptoms.The first step in treating the condition is applying a damp cloth shortly after the skin problem first shows to make sure that all of the irritant has been removed from the area. In some cases, the best treatment is to do nothing to the area.
In mild to moderate cases, patients may use skin creams containing corticosteroids to reduce the inflammation. These creams should be used carefully and according to the instructions they come with because when overused over longer periods of time they can cause serious skin conditions. Also, calamine lotion and cool oatmeal
Oatmeal
Oatmeal is ground oat groats , or a porridge made from oats . Oatmeal can also be ground oat, steel-cut oats, crushed oats, or rolled oats....
baths may relieve itching.. Over the counter diphenhydramine by mouth is helpful for night time itching.
Usually, severe cases are treated with systemic corticosteroids which may be tapered gradually, with various dosing schedules ranging from a total of 12 - 20 days to prevent the recurrence of the rash as well as a topical corticosteroid. Tacrolimus ointment or pimecrolimus cream can also be used additionally to the corticosteroid creams or instead of these. Oral antihistamines such as diphenhydramine or hydroxyzine may also be used in more severe cases to relieve the intense itching. Topical antihistamines are not advised as there might be a second skin reactions from the lotion itself.
The other symptoms caused by allergic contact dermatitis are generally eased with wet dressings and drying lotions to stop the itching. In most cases however, medication or actual treatment is not required as long as the trigger has been identified and avoided. The discomfort caused by the symptoms may be relieved by wearing smooth-textured clothing to avoid more skin irritation or by avoiding soaps with perfumes and dyes.
Commonly, the symptoms may resolve without treatment in 2 to 4 weeks but specific medication may hasten the healing as long as the trigger is avoided. Also, the condition might become chronic if the allergen is not detected and therefore it is not avoided.
Diagnosis
Diagnosing allergic contact dermatitis is primarily based on physical exam and medical historyMedical history
The medical history or anamnesis of a patient is information gained by a physician by asking specific questions, either of the patient or of other people who know the person and can give suitable information , with the aim of obtaining information useful in formulating a diagnosis and providing...
. In some cases doctors can establish an accurate diagnosis based on the symptoms that the patient experiences and on the rash's appearance. In the case of a single episode of allergic contact dermatitis, this is all that is necessary. Chronic and/or intermittent rashes which are not readily explained by history and physical exam often will benefit from further testing. A patch test (contact delayed hypersensitivity allergy test) is a commonly used examination to determine the exact cause of an allergic contact dermatitis. According to the American Academy of Allergy, Asthma, and Immunology, "patch testing is the gold standard for contact allergen identification".
The patch test consists in applying small quantities of potential allergens to small patches and which are then placed on the skin. After two days, they are removed and if a skin reaction occurred to one of the substances applied, a raised bump will be noticeable underneath the patch. The tests are again read at 72 or 96 hours after application.
Patch testing is used for patients who have chronic, recurring contact dermatitis. Other tests that may be used to diagnose contact dermatitis and rule out other potential causes of the symptoms include a skin biopsy and culture of the skin lesion.
Further reading
- A list of common allergens is shown in Table III in: