Allergic Contact Dermatitis (Chapter 14)

Pathogenesis of ACD

ACD is a delayed-type hypersensitivity response. It is an allergenspecific reaction that requires prior sensitization of the individual to the chemical in question. The pathogenesis of ACD involves an initial sensitization phase when the patient first comes in contact with the chemical, which penetrates the skin and then elicits a cascade of events that results in sensitization (see Ch. 4 for details). The subsequent re-exposure of the skin leads to the presentation of the responsible allergen to an already primed T-cell milieu, causing the release of multiple cytokines and chemotactic factors and resulting in the clinical picture of eczema. Once sensitized, all that is needed to elicit a reaction is contact with a low concentration of the causative chemical.

Bacitracin - has bacterial activity against what organisms? - often has co-reactivity with what?

Bacitracin is a topical antibiotic with activity against Gram-positive bacteria and spirochetes. It is used in topical antibacterial creams or ointments as well as in otic and ophthalmic preparations. Bacitracin is commonly used in combination with other topical antibiotics and corticosteroids (see above). It is frequently used in combination with neomycin, and although the two antibacterial agents are chemically unrelated, they often show co-reactivity. This is believed to be due to sensitization to both, as they are so frequently combined in OTC products (e.g. Neosporin®)28. In addition to ACD, bacitracin rarely causes anaphylaxis and/or contact urticaria

Methylisothiazolinone - found in what products?

By 2014, patch test clinics around the world were reporting that MI was becoming their most common allergen20. MI was previously used in combination with methylchloroisothiazolinone (MCI) in a ratio of 3 : 1 in rinse-off products, and its concentration was <3.75 ppm. In 2005, however, regulatory changes allowed its concentration to increase to 100 ppm, and this was followed by the current epidemic. While there is increasing recognition that use of sanitary wet wipes can lead to ACD of the anogenital region and hands (see Fig. 14.8B), it should be noted that MI has also been found in make-up removal wipes (see Fig. 14.6B), sorbolene lotions, liquid soaps, shampoos, deodorants, and a number of other personal care items21. Paints containing MI have been associated with occupational ACD as well as airborne ACD22.

Cobalt - 80% of patients with a cobalt allergy have cross reactivity with what? - what is "Poral"

Cobalt is a metal that is often used in conjunction with other metals in order to add hardness and strength. It is frequently combined with nickel, chromium, molybdenum, and tungsten. This may be the explanation for the frequent finding of sensitization to cobalt in patients who are also allergic to either nickel or chromium. Specifically, ~80% of individuals with a cobalt sensitivity have a co-sensitivity to nickel (more common in women) or chromate (more common in men)13. Exposure to cobalt is typically through a metal, most often in jewelry, snaps, buttons, or tools. However, cobalt is also found in cosmetics, hair dyes, orthopedic implants, ceramics, and enamel as well as in cement, paints, and resins13. Exposure can come from hobbies such as pottery making and occupations such as bricklaying. When patch testing to cobalt, one may see a particular reaction, described as "poral", that appears as erythematous to violaceous dots. This is not an allergic reaction but is believed to result from the allergen residing within the acrosyringia31. A cobalt spot test has recently been released, based on disodium-1-nitroso-2-naphthol-3,6-disulfonate

corticosteroids - classified into how many groups - which group has the most allergies?

Corticosteroids are administered in many different forms: topical, intralesional, oral, intramuscular, intravenous, inhalational, and intraarticular. They are anti-inflammatory agents and have been shown to cause ACD in 0.2-6% of patients40. Corticosteroids have been reclassified into three groups based on patch test results and molecular modeling, with group 1 corticosteroids producing the most allergic reactions41 (Table 14.11). It is suspected that ACD to these agents may be underdiagnosed, either because of insufficient testing to the allergens or perhaps owing to incomplete testing, as a later reading is often necessary because of the anti-inflammatory nature of these compounds40. Clinical scenarios that should raise the question of a possible allergy to topical corticosteroids include chronic dermatitis, failure to clear with topical corticosteroids, and exacerbation of dermatitis after use of topical corticosteroids. The combination of tixocortol-21-pivalate and budesonide provides reasonable screening for corticosteroid allergy (see Table 14.11), with ~75% of corticosteroid allergic reactions detected with these allergens in one large study40. Positive patch test reactions to corticosteroids are often unexpected in routine testing, but are usually relevant. They are often seen with other positive reactions. Fig. 14.18 may help direct the clinician in approaching the patient suspected of having an ACD to topical corticosteroids. In addition to the anti-inflammatory nature of corticosteroids complicating patch test interpretation, an edge effect has also been observed. During the first reading, there may be erythema only at the rim of the test chamber, with a clear center that may later become involved. This is believed to be due to the anti-inflammatory effect of corticosteroids. In the center, the corticosteroid may be concentrated, inhibiting a reaction, but be less concentrated at the rim, where a reaction may occur more readily

Formaldehyde

Formaldehyde is ubiquitous. It is a colorless gas that can be found in the workplace as well as in cosmetics, medications, nail hardeners, textiles, paints, cigarette smoke, paper, and formaldehyde resins (e.g. plastic bottles)33. Formaldehyde can cause several different types of reactions, including ICD, ACD, contact urticaria, and mucous membrane irritation, especially of the conjunctiva and respiratory tract. Formaldehyde is present in the air, as it is released in cigarette smoke, automobile exhaust, and even hair-straightening products. Today, formaldehyde is rarely used in personal care products or cosmetics. However, allergy to formaldehyde is commonly seen in association with other formaldehyde-releasing preservatives, such as quaternium-15, imidazolidinyl urea, diazolidinyl urea, DMDM hydantoin, 2-bromo-2-nitropropane-1,3-diol, and tris(hydroxymethyl)nitromethane, and therefore formaldehyde-sensitive individuals should generally avoid these substances33. Textile dermatitis can be caused by formaldehyde resins, because the latter are used as a finish on "wash-and-wear" or wrinkle-resistant clothes. Of the various textiles, 100% polyester is believed to have the least amount of formaldehyde13. A study of many fabrics showed that some free formaldehyde was present in all of those tested13. Washing clothes, especially those that are "permanent press" or "drip dry", several times prior to wearing will decrease the amount of formaldehyde present but will not eliminate it. As formaldehyde is so widespread, avoidance is often difficult. Clinical relevance can sometimes be difficult to determine.

Fragrance Mix

Fragrances are ubiquitous in our environment. They are used to provide a pleasant odor and have been used extensively for centuries. Fragrances were identified as the second most common allergen according to the NACDG, with a rate of 11.9%7. The detection of a fragrance allergy was made easier with the introduction of a fragrance mix in the 1970s. Prior to that, fragrance allergy was identified primarily through testing with balsam of Peru, whichd etected only about 50% of those affected23. The current fragrance mix I contains eight different fragrance components (at 1% each; Table 14.10). Fragrance mix I is the most useful tool for detecting fragrance allergy24. However, the composition of fragrance-containing products continually changes. Therefore, by including additional allergens such as those in fragrance mix II (see Table 14.10), the detection rate of fragrance allergy can be increased. It is estimated that ~25% of patients allergic to fragrance would be missed if fragrance mix II were not used25. in product formulations, fragrances can be used to provide a pleasant odor. However, they can also be used to mask an unpleasant odor - a so-called masking fragrance. This often occurs in products labeled "unscented". Patients who are identified as being allergic to fragrance must be instructed to read all labels and to avoid any product that lists a fragrance, is labeled "unscented", or has an obvious scent (see Fig. 14.15). They should be instructed to look instead for "fragrance-free" products. Unfortunately, there are several fragrance ingredients that have other purposes, i.e. they act as a preservative or emollient. These covert fragrances, e.g. balsam of Peru, benzylaldehyde, benzyl alcohol, bisabolol26, can be used in a product and the product may still be labeled fragrance-free as long as the potentially allergenic ingredient has been identified as being used for a purpose other than fragrance. Obviously, this causes significant problems for the individual with fragrance allergy who is trying to avoid fragrances. Label reading may not always be enough unless the patient is educated about some of these practices. Complete disclosure on labels of all ingredients regardless of intended function would be helpful, but this is not yet part of industry practice in the US; by contrast, in Europe 26 fragrances must be included in the product label27. For the individual allergic to fragrances, repeat open application testing is very helpful in screening for an allergy to new or old products.

Allergic contact derm

Irritant contact dermatitis (ICD) accounts for ~80% of all contact dermatitis (see Ch. 15), with allergic contact dermatitis (ACD) accounting for the remainder1. ACD is a delayed-type hypersensitivity reaction that is elicited when the skin comes in contact with a chemical to which an individual has previously been sensitized The classic picture of contact dermatitis is a well-demarcated, erythematous, vesicular and/or scaly patch or plaque with well-defined margins corresponding to the area of contact (Fig. 14.1A). The distribution can be linear, when an object such as a leaf or branch is rubbed against the skin (Fig. 14.1B), or localized to the site where there has been contact with the offending chemical or product, e.g. hand dermatitis caused by ACD to epoxy resin or foot dermatitis due to ACD to the components of shoes

Eyelid contact Derm - name the most common allergens?

Most Common allergens • Fragrances, including Myroxylon pereirae (balsam of Peru) • Preservatives - quaternium-15, DMDM hydantoin, methylchloroisothiazolinone, methyldibromoglutaronitrile • Topical antibiotics - neomycin • Metals - nickel, cobalt chloride, gold sodium thiosulfate • Surfactants - cocamidopropyl betaine, amidoamine

Myroxylon pereirae - aka, what is it? - seen in individuals with allergy to what? - these patients should be counseled to avoid what?

Myroxylon pereirae (balsam of Peru) is a naturally occurring fragrance that is the seventh most common allergen identified by the NACDG7. The International Fragrance Association has recommended that balsam of Peru should not be used as a fragrance ingredient. Allergy to balsam of Peru is most commonly observed in those with fragrance allergy, but it is also seen in those with allergies to spices, particularly cloves, Jamaican pepper, and cinnamon. Patients with a positive reaction to balsam of Peru should be counseled to avoid fragrances. Occasionally, spices and sources such as colas, tobacco, wines, and vermouth can be the culprit in patients with an allergy to balsam of Peru.

Neomycin - commonly co reacts with what?

Neomycin is an antibiotic that is prescribed as a topical rather than an oral medication because it has poor gastrointestinal absorption. It is the most commonly used topical antibiotic and is the most common sensitizer among the topical antibiotics7,13. Neomycin is found in many over-the-counter (OTC) preparations, including antibacterial ointments, hemorrhoid creams, and otic and ophthalmic preparations (see Table 14.2). It is frequently used in conjunction with other antibacterial agents, such as bacitracin and/or polymyxin, as well as with topical corticosteroids. Co-reactivity is commonly observed with neomycin and bacitracin. These antibiotics are not chemically related and

Nickle - How common, + on what % of patch tests? - nickel dermatitis occurs commonly where? - what test is used to identify products containing nickel - these patietns cant wear which precious metal?

Nickel ranks as the most common allergen tested by the NACDG, with 20.1% of patch test clinic patients reacting to it. it has been proposed that the high rate of nickel sensitivity, which in some patch test clinics approaches 30-40%, can be attributed in large part to ear piercing. Clinically, nickel dermatitis most commonly occurs at sites of contact with earrings, necklaces, and the backs of watches (see Fig. 14.9A). Dermatitis of the mid-abdomen caused by a belt buckle or snap is common (Fig. 14.16A) and eyelid dermatitis from metal eyelash curlers or eyeglasses can also be seen. Facial dermatitis due to ACD to nickel and chromate within cellular phones has been described as has a generalized eruption caused by nickel from an iPad18. Concomitant reactions to nickel and cobalt have been reported and may be due to the frequency with which the two metals are used in combination19. Of note, sweating can increase the amount of metal leached from a product. A useful test to determine whether a particular item contains nickel is the dimethylglyoxime test (see Appendix), which identifies objects that release nickel using a pink color indicator (Fig. 14.16B). Individuals with nickel allergy should avoid costume jewelry. They can usually wear jewelry made of stainless steel, platinum or gold, but not white gold. Some clinicians advocate coating nickel-containing surfaces such as snaps on jeans with clear nail polish (e.g. Beauty Secrets Hardener) to prevent leaching by sweat onto the skin. However, the nail polish can rub off and should be reapplied if it is effective.

P-Phenylenediamine - an allergen in what setting?

Paraphenylenediamine (PPD) is the most commonly used permanent hair colorant and it is recognized as a common cause of ACD. Once fully oxidized, the disperse dye is no longer allergenic, but in reality the chemical is not always fully oxidized. Since 1998, PPD has been found in some temporary tattoos in concentrations higher than those present in hair color products35. As a result, PPD has resurfaced as an allergen in a new population (Fig. 14.17). When ACD is due to PPD in permanent hair colorants, it involves primarily the forehead, neck and scalp.

Quaternium-15 - used as what? has antibacterial affects against what? - typically plays a role as an allergen in what setting? - proposed mechanism for causing allergy? cross reactivity with what?

Quaternium-15 is a quaternium compound that is used as a preservative. It is an effective biocide against Pseudomonas aeruginosa and P. cepacia, as well as other bacteria and fungi. Although quaternium-15 is used in several industries, the incidence of associated occupational contact dermatitis is very low33. Quaternium-15 more typically plays a role as an allergen in personal care products such as shampoos, moisturizers, conditioners, and soaps. In the past, quaternium-15 and formaldehyde were reported to be the most common cosmetic preservatives to cause ACD in the US, but they have been overtaken by MI. The allergenicity of quaternium-15 can be due to its release of formaldehyde34. Studies have shown that up to 80% of those reacting to quaternium-15 are also formaldehyde-sensitive30,31. Allergy to quaternium-15 is often relevant to the patient's dermatitis30,31. In addition to coexisting with formaldehyde sensitivity, allergy to quaternium-15 can be seen in association with other formaldehyde-releasing preservatives, such as imidazolidinyl urea, diazolidinyl urea, 2-bromo-2-nitropropane-1,3-diol, DMDM hydantoin, and tris(hydroxymethyl)nitromethane13,28,33,34. Avoidance of quaternium-15 is possible through careful label reading. If the individual allergic to quaternium-15 is not allergic to the other formaldehyde-releasing preservatives mentioned above, they need only avoid quaternium-15. Obviously, avoidance of the other formaldehyde-releasing preservatives may be necessary depending on the patch test results. Quaternium-15, formaldehyde, diazolidinyl urea, and imidazolidinyl urea are present in T.R.U.E. TEST®. However, other formaldehyde-releasing preservatives may be missed if expanded patch testing beyond the T.R.U.E. TEST® is not performed (see Table 14.3). As a group, the quaternium amino compounds are infrequent sensitizers and the other quaternium compounds can be safely used in those allergic to quaternium-15

Rubber Chemicals

Rubber accelerators are important causes of hand dermatitis caused by gloves, particularly in healthcare workers. Allergens include thiurams, carbamates, mercaptobenzothiazole and its derivatives, and thioureas. In Europe, as well as the US, there has been little change in either sensitization patterns or sensitization frequencies45. ACD to rubber may coexist with an immediate hypersensitivity to natural rubber latex protein (see Ch. 16).

Systemic Corticosteroids

Systemic exposure to a chemical may result in a widespread dermatitis. This reaction generally involves a chemical to which the patient has had a prior contact allergy; the patient is then exposed to the same chemical (or one that cross-reacts) via a systemic route, such as with an injection or oral, intravenous or intranasal administration. This reaction is believed to be due to a delayed T-cell-mediated immune response. Historically, one of the most common examples of systemic contact dermatitis was the patient with a history of ACD to ethylenediamine who then developed a diffuse dermatitis secondary to intravenous aminophylline, which contains ethylenediamine (Fig. 14.19). Other causes of systemic contact dermatitis due to ingestion of allergens that have previously caused an ACD include antibiotics, corticosteroids, plants/plant products, propylene glycol, sorbic acid, and importantly, metals46-53. Marks et al.46 reported the ingestion of cashews tainted with oil from the cashew nut shell resulting in a systemic contact dermatitis in patients with a prior history of poison ivy dermatitis. In addition, ingestion of a pesto sauce made with cashew nuts resulted in systemic contact dermatitis in the form of the "baboon syndrome" (symmetric, sharply demarcated erythema of the gluteal or inguinal area plus other intertriginous or flexural sites)47. Ingestion of both cashews and mangoes has been shown to cause reactions in patients sensitive to poison ivy and poison oak, as they are all members of the Anacardiaceae family (see Ch. 17). In the proper clinical setting, patch tests demonstrating a sensitivity to balsam of Peru or fragrance mixture can support the diagnosis of a systemic contact dermatitis due to balsam-related foods or spices. A diet avoiding such foods or spices may result in an improvement of the dermatitis53

Textile Dermatitis - what are the common allergens in textile dermatitis

Textile dye dermatitis often goes undetected because of low suspicion and a lack of routine testing with screening allergens. The allergens most likely to cause textile dermatitis are not the synthetic or natural fibers from which the textiles are made, but rather the dyes used tocolor them and the resins (e.g. ethyleneurea/melamine formaldehyde resin, dimethylol dihydroxyethyleneurea) used to make clothes less likely to wrinkle or shrink43,44. Textile dermatitis typically occurs in areas where clothing fits more tightly (see Fig. 14.9C), and it is more common in women43. Dyes, particularly disperse blue dyes 106 and 124, have been found to be a common cause of textile dermatitis and can be used as screening agents43. They frequently cross-react and positive patch test reactions can be delayed up to 7-10 days44. Although p-phenylenediamine is a disperse dye, it is not a good screening allergen for textile dye dermatitis44. Testing with an individual's garment can also produce a relevant positive patch test reaction.

Patch Testing - what is the main brand test used? how many allergens does it test? how often does this particular test identify a patients allergen? - Use of topical steroids, oral steroids, antihistamines

The T.R.U.E. TEST®, which is approved by the US Food and Drug Administration (FDA), consists of panels with pre-impregnated allergens, allowing for increased ease of use and perhaps resulting in increased patch testing. However, it currently screens for 36 allergens, including a negative control, and although this is helpful, extended testing beyond these allergens has been shown to improve diagnostic accuracy6-8. With extended testing, 37-76% more positive reactions were detected, and 47% of the patients had positive reactions only to non-screening allergens6-8 (these latter allergens come in multi-use syringes or tubes [see Appendix]). Lastly, when patch testing was performed with 28 T.R.U.E. TEST® allergens, only 27.6% of patients had completely detected allergens8. Prior to the application of the patch tests, the clinician should ask questions about exposures both at home and at work, and attempt to understand the mechanics of the work environment. The effect of vacations and time away from work or home should also be ascertained. In addition, all personal care products should be inventoried and hobbies explored. The information gained can help to direct allergen selection more appropriately. The patient should not have a sunburn in this area and should not have applied topical corticosteroids to the sites of patch testing for 1 week10,11. Systemic and longer-lasting injectable corticosteroids should also be avoided for at least 1-2 weeks. For disease control, the daily oral AM dose of corticosteroids should not exceed the equivalent of 20 mg of prednisone during testing.) Any one of these factors may decrease the individual's ability to elicit a reaction when challenged by an allergen, resulting in a false-negative test

Ddx

The differential diagnosis of ACD includes many other forms of dermatitis, such as ICD, protein contact dermatitis, atopic dermatitis, stasis dermatitis and seborrheic dermatitis, as well as the erythematous form of rosacea. Hand and foot ACD also needs to be distinguished from endogenous dermatitis, psoriasis, and tinea (see Table 13.4 & Fig. 15.6). Of note, these conditions may coexist, which can make clinical assessment complicated. In general, when evaluating regional dermatoses (e.g. eyelid, hand and foot), other disorders common to the area need to be considered as well as allergens specific to that area (Table 14.2). If there is widespread disease, either because of widespread contact with an allergen or autosensitization, additional causes of erythroderma (see Ch. 10), e.g. Sézary syndrome, enter the differential diagnosis.

Systemic Contact Derm

The ingestion of metals can also cause systemic contact dermatitis, and nickel is the metal most commonly implicated48,49. However, the use of low-nickel diets to treat dermatitis in patients with positive patch tests to nickel is controversial, although there is increasing interest54. The possibility of systemic contact dermatitis to metals in orthopedic implants has also been suggested, along with proposed screening recommendations (Fig. 14.20)55. Nonetheless, for several reasons, including the likelihood that immune reaction pathways are different for implants compared to the skin, the role of lymphocyte transformation testing remains unclear, and patch testing may neither predict future problems nor aid in the decision to remove an existing implant, this remains a topic of debate. Lastly, Fowler reported a patient with systemic contact dermatitis following ingestion of chromium picolinate, a nutritional supplement56. Patch testing was positive to potassium dichromate, and upon discontinuation of the chromium picolinate, the dermatitis subsided. Examples of other cutaneous allergens and their common sources of systemic exposure are listed in Table 14.12. An extensive chapter on this subject is in Fisher's Contact Dermatitis textbook48 and the reader is referred there for additional information.

Top Allergens - what are the top ten allergens? - what are the top allergens in kids?

The top 10 allergens, as identified by the North American Contact Dermatitis Group (NACDG) in 2013-2014, were nickel sulfate, fragrance mix I, methylisothiazolinone (MI), neomycin, bacitracin, cobalt chloride, Myroxylon pereirae (balsam of Peru), p-phenylenediamine, formaldehyde, and methylchloroisothiazolinone/MI. It should be noted that the list contains three preservatives, two metals, two topical antibiotics, two fragrance components, and one dye Top allergens in kids: Metals - nickel sulfate, cobalt chloride*, potassium dichromate† Preservatives - quaternium-15, formaldehyde, methylchloroisothiazolinone/ methylisothiazolinone, 2-bromo-2-nitropropane-1,3-diol (Bronopol®) Topical antibiotics - neomycin sulfate, bacitracin Fragrances - fragrance mix I, fragrance mix II, Myroxylon pereirae (balsam of Peru) Components of rubber products - carba mix Other - lanolin alcohol, propylene glycol, p-phenylenediamine, carmine, propolis, decyl glucoside (surfactant), Compositae mix

Clinical Presentation Histology

The typical appearance is often a well-demarcated pruritic eczematous eruption, which may be acute (blistering, weeping and/or edema)) or chronic (lichenified or scaly plaques).This reaction is typically localized to the area of skin that comes in contact with the allergen. Histologically, ACD is the prototype of spongiotic dermatitis. In the acute stage, there is a variable degree of spongiosis, with a mixed dermal inflammatory infiltrate containinglymphocytes, histiocytes and a variable number of eosinophils. In moderate to severe reactions, marked spongiosis results in intraepidermal vesiculation

Thimersol - can be found in what?

Thiosalicylic acid and ethylmercuric chloride are the two components that are combined to form thimerosal - sodium ethylmercurithiosalicylate - a preservative that is used in a few products. It is believed that the most likely cause of sensitization to thimerosal comes from its use as a preservative in vaccines36. Reports of sensitivity to ethylmercuric chloride and thiosalicylic acid have been published and both compounds have been found to be capable of inducing a delayed hypersensitivity reaction36. Many positive reactions to thimerosal are found on patch testing. Clinical relevance may be found in patients who use otic or ophthalmic drops, but in general relevance is low. Currently, thimerosal is in neither the NACDG 70 Series nor the European Baseline Series (see Table 14.3), but is still present in the T.R.U.E. TEST®.

Airborne Contact Derm - common causes of airborne contact derm - common distribution

When airborne allergens have contact with the skin, they may cause ACD or ICD, with a resemblance (or overlap) with photoallergic contact dermatitis and phototoxic contact dermatitis (see Fig. 87.15). Ragweed dermatitis, a good example of an airborne contact dermatitis, is most noticeable on the face (see Ch. 17)57. Prolonged and repetitive exposure to airborne allergens generally produces an ACD that is lichenified and dry and is predominantly located in the exposed portions of the skin: especially the eyelids, but also the face, V of the neck, arms, and legs58. The most common causative agents are plants, especially Compositae allergen, natural resins, woods, plastics, rubbers, glues, metals, pharmaceutical chemicals, insecticides and pesticides59. Airborne ACD has been associated with a wide range of allergens, from common allergens such as plants (see above) and epoxy chemicals (Fig. 14.21) to more obscure causes such as essential oils volatilized during aromatherapy and thyme dust in farmers, to name but a few60-62. There has been an increasing number of reactions to paints, especially to those containing MI or MCI62,63, as well as to baby wipes64. Occupationally induced reactions appear to be the most common cause of airborne contact dermatitis. Dermatoses in exposed areas should raise the possibility of a possible airborne contact allergy, leading to a series of questions regarding possible exposure sources and to appropriate patch testing when indicated.

GOLD - mostly seen in what patients? - have higher rates of what concomitant allergy -

Worldwide rates of positive gold reactions vary, and with routine testing they range from 0.78% to 10%37,38. In one NACDG series, 90% of gold-allergic patients were women, and there appeared to be a higher rate of nickel (33.5%) and cobalt allergies (18%) in patients with gold allergy than in the general population (14% and 9%, respectively)39. Similar findings have been reported in other studies38. When relevant, the most common clinical presentation is that of a hand, facial, or eyelid dermatitis37,39. One of the difficulties with gold patch testing is that the relevance of positive reactions is usually difficult to determine37-39. Gold sodium thiosulfate is currently not included in the NACDG 70 Series or the European Baseline Series

Patch testing application - when are the patches read? - what are you looking for with the second reading?

the patient is sent home with instructions to keep the back dry and the patches secured until the second visit at 48 hours. Patients should also be told to avoid excessive sweating and to avoid heavy lifting, as the patches may come loose. Antihistamines can be prescribed, as they will not affect the outcome of the testing. Patches are removed at 48 hours. The patient is again asked to keep the back dry until the second reading, which can be performed from 72 hours to 1 week after the initial application of patches. When the patient returns for the second reading, the map is used to identify any positive reactions. This later reading is necessary as patch test responses to some allergens such as gold, neomycin, and corticosteroids may be delayed +/− Doubtful reaction, faint macular erythema + Weak, non-vesicular reaction with erythema, infiltration and papules ++ Strong, vesicular reaction with erythema, infiltration and papules +++ Spreading bullous reaction − Negative reaction IR Irritant reaction