ALLERGIC CONTACT
URTICARIA
Allergic contact urticaria (ACU) represents one of the least common forms of contact dermatitis. ACU is an immunoglobulin E-mediated immediate-type hypersensitivity reaction that is distinct from the T cell-mediated type IV hypersensitivity reaction of ACD. Importantly, ACU has been reported in response to a number or agents that are also capable of eliciting a type IV reaction, for example, bacitracin (antibiotic), mercaptobenzothiazole (rubber accelerator), and colophony (adhesive).
The most notorious allergen to cause ACU worldwide is natural rubber latex. The incidence in the United States is largely unknown; however, estimates suggest that less than 1 percent to 2 percent of the general population is affected. Among hospital workers most likely to be exposed to natural rubber latex gloves, the rate of latex ACU has been reported to range from a low of 5.5 percent to as high as 38 percent. Furthermore, co-morbid conditions requiring hospitalizations and medical care in early life, such as moderate to severe atopic dermatitis, spina bifida, or meningomyelocele, predispose to the development of ACU, as does mucosal exposure to latex.
ACU from latex may present as immediate symptoms (such as burning, stinging, or itching with or without localized urticaria on contact with latex proteins) or, with aerosolization exposure, may include disseminated urticaria, allergic rhinitis, and/or anaphylaxis. Latex-allergic patients may also develop a type IV delayed hypersensitivity reaction to nonlatex components of the gloves, usually on the dorsal aspect of the hands; for example, to a rubber additive (thiuram) that may be found in latex, nitrile, and vinyl gloves. In contrast to ACD, ACU in response to latex gloves may present with palmar involvement, which may relate to solubilization of the latex proteins or the lipid content of the hyperkeratotic volar surface caused by normal hidrosis.
Although there are over 250 separate natural rubber latex proteins, only approximately 25 percent show reactivity with immunoglobulin E autoantibodies.46 As of 2003, the International Union of Immunological Societies Committee on Nomenclature listed 13 Hevea brasiliensis (Hev b) protein allergens. Significant advances in DNA technology and cloning have allowed for purification and characterization of these allergens. It is now known that the most important Hev b allergens are Hev b 1 to 3
for children with spina bifida and Hev b 2 and 5 to 7 for health care workers.
A diagnosis of latex allergy should be considered in any patient with a history of urticaria or angioedema when donning condoms or gloves, or inflating balloons. In vitro radioallergosorbent testing and enzyme-linked immunosorbent assay are commercially available and should be performed as the initial diagnostic step. Three in vitro serologic assays have U.S. Food and Drug Administration (FDA) approval for diagnostic purposes: ImmunoCAP (Pharmacia-Upjohn, Uppsala, Sweden), AlaSTAT FEIA (Diagnostic Products Corp., Los Angeles, CA), and HY-TEC EIA (Hycor Biomedical, Inc., Garden Grove, CA).
Although skin prick testing is the gold standard, it should be noted that there is currently no FDA-approved, commercially available, standardized latex allergen preparation. The stability profile and quality controllability of non-ammoniated latex make it the current top candidate for FDA licensure. Currently, extemporaneous extracts or elutes made by soaking high-allergen gloves in water at room temperature are used. In most but not all cases, these crude eluates are sufficient to allow prick test confirmation of ACU. It must be emphasized that in vivo testing can potentiate anaphylactic reactions
Prevalence/Percentage of Subjects Showing Positive Reactions to Allergens Tested by the North American Contact Dermatitis Group
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1. Nickel sulfate (2.5%)a
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16.7
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2. Neomycin (20%)
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11.6
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3. Balsam of Peru (25%)
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11.6
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4. Fragrance mix (8%)
|
10.4
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5. Thimerosal (0.1%)b
|
10.2
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6. Sodium gold thiosulfate (0.5%)a
|
10.2
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7. Quaternium-15 (2%)b
|
9.3
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8. Formaldehyde (1% aqs)b
|
8.4
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9. Bacitracin (20%)
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7.9
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10. Cobalt chloride (1%)a
|
7.4
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11. MDGN/PE (2.5%)b
|
5.8
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12. Carba mix (30%)c
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4.9
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13. Para-phenylenediamine (1%)
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4.8
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14. Thiuram (1%)c
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4.5
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15. Potassium dichromate (0.25%)a
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4.3
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16. Benzalkonium chloride (1% aqs)b
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4.3
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17. Propylene glycol (30% aqs)
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4.2
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18. 2-Bromo-2-nitropropane-1,3-diol (0.5%)b
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3.3
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19. Diazolidinylurea (1% aqs)b
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3.2
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20. Imidazolidinylurea (2%)b
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3.0
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21. Tixocortol-21-pivalate (1%)
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3.0
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22. Disperse Blue 106 (1%)
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3.0
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23. Ethylenediamine dihydrochloride (1%)
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2.8
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24. DMDM hydantoin (1%)b
|
2.8
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25. Cocamidopropyl betaine (1% aqs)
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2.8
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26. MDGN/PE (4%)b
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2.7
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27. Colophony (20%)
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2.6
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28. Epoxy resin (1%)
|
2.3
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29. MCI/MI (100 ppm aqs)b
|
2.3
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30. Amidoamine (0.1% aqs)
|
2.3
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31. EU/MF resin (5%)
|
2.3
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32. Lanolin (30%)
|
2.2
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33. p-tert-Butylphenol formaldehyde resin (1%)
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1.9
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34. Glyceryl thioglycolate (1%)
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1.9
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35. Benzocaine (5%)
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1.7
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36. Tolsylamide formaldehyde resin (10%)
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1.6
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37. Methyl methacrylate (2%)
|
1.4
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38. Glutaraldehyde (1%)b
|
1.4
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39. Ethyl acrylate (0.1%)
|
1.3
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40. dl-α-Tocopherol
|
1.1
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41. Budesonide (0.1%)
|
1.1
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42. DMDHEU (4.5% aqs)
|
1.1
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43. Ylang-ylang oil (2%)
|
1.1
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44. Black rubber mix (6%)c
|
1.0
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45. Compositae mix (6%)
|
1.0
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46. Mercaptobenzothiazole (1%)c
|
0.9
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47. Dibucaine (2.5%)
|
0.9
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48. Thioureas (1%)
|
0.8
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49. Jasmine absolute (2%)
|
0.7
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50. Mercapto mix (1%)c
|
0.7
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51. Lidocaine (15%)
|
0.7
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52. Paraben mix (1%)b
|
0.6
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53. Sesquiterpene lactone (0.1%)
|
0.6
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54. Benzophenone (3%)
|
0.6
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55. PCMX (1%)b
|
0.6
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56. Tetracaine (1%)
|
0.6
|
57. Hydrocortisone-17-butyrate (1%)
|
0.5
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58. dl-α-Tocopherol acetate
|
0.5
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59. IPBC (0.1%)
|
0.3
|
60. PE (1%)b
|
0.2
|
61. Prilocaine (2.5%)
|
0.1
|
aqs = aqueous; DMDHEU = dimethyloldihydroxyethyleneurea; DMDM = dimethylol-dimethyl; EU/MF = ethyleneurea/melamine formaldehyde; IPBC = iodopropynyl butyl carbamate; MCI/MI = methylchloroisothiazolinone/methylisothiazolinone; MDGN = methyldibromo glutaronitrile; PCMX = parachlorometaxylenol; PE = phenoxyethanol.
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a Metal allergen.
b Biocides/preservatives.
c Rubber additive.
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Bold indicates components of T.R.U.E. (Thin-layer Rapid Use Epicutaneous) Test. (T.R.U.E. Test uses caine mix instead of benzocaine.)
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North American Contact Dermatitis Group. Am J Contact Dermatol 15:176, 2004.
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