Epicutaneous test

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Synonym(s)

Allergy test; Atopy patch test; Epicutaneous standard test; Epicutaneous testing; Lapping test; patch test; Patch test; Standard test series; Standard test series for children

Definition
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Primary, largely standardized test for the diagnosis of an allergic late type reaction of the eczema type (see below allergy), especially in allergic contact eczema. For the composition of the standard series for adults and children see table.

General information
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The frequency of allergic contact eczema in children is reported to be between 5-20%. Children < 6 years of age should only be selectively tested if there is a strong suspicion of allergic contact dermatitis, > 12 years the test can be performed according to the recommendations for adults.

According to the recommendations of the German Contact Allergy Group (DKG, valid since 1.1.2014), the standard test series for adults is composed as follows ( cited in Mahler V. 2015)

Test substances Test concentrations Test bases

  1. Potassium dichromate 0,5 % Vaseline (Vas.)
  2. Thiuram mix 1 % Vas.
  3. Cobalt (II) chloride, 6*H20 1 % Vas.
  4. Peru balsam 25 % Vas.
  5. Colophony 20 % Vas.
  6. N-Isopropyl-N'-phenyl-p -phenylenediamine 0,1 % Vas.
  7. Wool wax alcohols 30 % Vas.
  8. Mercapto mix without MTB 1 % Vas.
  9. Epoxy resin 1 % Vas.
  10. Nickel (II) sulphate 5 % Vas.
  11. Methylisothiazolinone 0,05 % Aqu.
  12. Formaldehyde 1 % Aqu.
  13. fragrance mix 8 % Vas. (see remark)
  14. Turpentine 10% Vas.
  15. (chlorine)-methyliso- thiazolinone (MCI/MI) 100 ppm Aqu.
  16. Paraben mix 16 % Vas.
  17. Cetylstearyl alcohol 20 % Vas.
  18. Zinc diethyldithiocarbamate 1 % Vas.
  19. Dibromodicyanobutane(Methyldibromo Glut.) 0,2 % Vas.
  20. Propolis 10 % Vas.
  21. Sandalwood oil 10 % Vas.
  22. Compositae Mix II 5 % Vas.
  23. Mercaptobenzothiazole 1 % Vas
  24. Lyral 5% Vas.
  25. Iodopropynyl butylcarbamate 0,2 % Vas.
  26. Fragrance Mix II 14 % Vas. (see remark)
  27. Sodium lauryl sulphate (SLS) 0,25 % Aqu.
  28. Ylang-ylang (I + II) oil 10 % Vas.
  29. Jasmine absolute 5 % Vas.

Note: The listed test substances are available in the epicutaneous test series" Fragrance Mix" and "Fragrance Mix II".

According to the recommendations of the German Contact Allergy Group (DKG) the standard epicutaneous test for children consists of the following substances:

  1. nickel sulphate
  2. Thiuram mix
  3. Rosin
  4. Mercaptobenzothiazole
  5. Fragrance mix I
  6. Fragrance Mix II
  7. Mercapto Mix
  8. Bufexamac
  9. Dibromdicyanobutane
  10. Chloromethylisothiazolinone
  11. Neomycin
  12. Composite Mix
  13. p-tert. butylphenol formaldehyde resin (only for shoe exposure)
  14. Potassium dichromate (only for shoe exposure)
  15. Wool wax alcohols (only for skin care products)
  16. Disperse blue mix (only for clothing)
  17. Paraphenylenediamine (only for henna tattoos).

The application time should be limited to 24 hours, further readings according to the recommendations for adults after 48 and 72 hours.

Implementation
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  • To avoid a toxic skin reaction, the allergen is worked into an indifferent base (usually Vaseline) in a highly diluted form and applied (glued) to the healthy skin of the back in small test chambers made of aluminium (e.g. Finn Chambers), thin-layer foils (True-Test) or cellulose. The test reaction is regularly read after 48 hours and 72 hours, occasionally also after 96 hours. In case of questionable clinical relevance, a so-called repeated open application test (ROAT) or use use test can also be performed, in which the allergen is tested daily on the inner side of the upper arm for 1 week. A further possibility for clarifying clinical relevance is the open application test in loco.
  • Evaluated:
    • - (no reaction = negative)
    • ? (questionable; only erythema, no infiltrate)
    • + (single positive reaction; only erythema possibly with low infiltrate; possibly discrete papules)
    • ++ (double positive reaction; erythema and papules, infiltrate, vesicles)
    • +++ (triple positive reaction; erythema, infiltrate, confluent vesicles)
    • ++++ (quadruple positive reaction; eroded vesicles; attributed by many allergologists to the triple positive reaction)
    • IR (irritative-toxic reaction; soap effect, vesicle, bladder, necrosis)
    • nt (not tested; allergen contained in a test block but not tested)
    • f (follicular reaction; they are to be assigned to the reactions in question in the evaluation).
  • The reaction dynamics of epicutaneous testing may be included in the assessment. A crescendo or plateau pattern speaks more for the allergic type, a decrescendo pattern more for the irritant type. In case of late reactions, which occur for the first time about 10-14 days after application of the epicutaneous test, an ("iatrogenic") sensitization by the test should be considered.
  • Positive reactions to structurally related substances may be cross-reactions.
  • If positive reactions (> 5) to chemically unrelated substances occur, this may be an expression of an individually increased sensitivity to the contact allergy. Alternatively, if there are numerous positive reactions, an Angry back/Excited Skin syndrome should always be considered. In such a case, many of the morphologically positive (+ to +++) reactions will be interpreted as false positive.
  • If the allergic reaction does not occur in the epicutaneous test despite clear anamnestic or clinical indications of the presence of sensitization, this gives rise to the suspicion of a "false negative" reaction. This may be due to the test method (too low allergen concentration, unsuitable vehicle, poor occlusion, too short reading sequence) or to the patient's reduced immunoreactivity (e.g. due to topical or systemic medication or UV light). In case of false positive reactions, e.g. in the context of an "excited skin syndrome", or if false negative reactions are suspected, the testing of the individual substances should be repeated at a later time, but if possible only after 2 months. Further procedures such as application tests (e.g. ROAT) can help to clarify sensitisation in the hands of experienced investigators.

Note(s)
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  • False positive epicutaneous reactions (possibly more than 5) in the sense of a so-called angry back by a massive test reaction to a strong contact allergen with a hematogenic scattering reaction into other (negative) test areas can occur if epicutaneous testing is performed too early on still eczematized skin or in case of an acute eczema attack. On the other hand, false negative test reactions are to be expected with iatrogenic T-cell suppression (internal steroid therapy, antihistamines, UVA therapy, etc.).
  • Silent sensitization: Positive epicutaneous test result without indication of a current or past allergic contact dermatitis.
  • After reading an epicutaneous test, an evaluation of the clinical relevance of the type IV sensitizations present must always be made. All information should then be documented for the patient in an allergy pass. It is useful to indicate the clinical relevance with reference to the allergen in the passport. The clinical relevance can be indicated by means of the so-called COADEX index. This index includes the most important, practice-relevant criteria.
  • The tear-off epicutaneous test is to be regarded as a modification. This is carried out e.g. to prove a continuing clinical suspicion of a contact allergy in case of a negative epicutaneous test.
  • Pregnancy and epicutaneous testing: According to the guideline no epicutaneous testing should be performed during pregnancy (possible permeation of allergens).
  • The authorities intend to evaluate the epicutaneous test in accordance with the guidelines of the German Drug and Drug Additive Ordinance ( AMWHV), also known as "Good Manufacturing Practice (GMP)". This means that ingredients of e.g. care products such as a body lotion should only be tested under GMP quality.

Literature
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  1. Bourke J et al (2001) Guidelines for care of contact dermatitis. Br J Dermatol 145: 877-885
  2. Bruynzeel DP et al (2004) Photopatch testing: a consensus methodology for Europe. J Eur Acad Dermatol Venereol 18: 679-682
  3. Darsow U et al (1997) Allergy and atopic eczema: on the value of the "atopy patch test". dermatologist 48: 528-535
  4. Devos SA et al (2002) Epicutaneous patch testing. Eur J Dermatol 12: 506-513
  5. Fartasch M et al. (2008) The mute sensitization in the review process - How could it be handled? JDDG 6: 34-39
  6. Kamphof WG (2003) Patch-test-induced subjective complaints. Dermatology 207: 28-32
  7. Pesonen M et al (2015) Patch test results of the European baseline series among patients with occupational contact dermatitis across Europe - analyses of the European Surveillance System on Contact Allergy network, 2002-2010 Contact Dermatitis 72:154-163
  8. Schnuch A et al. (2012) Allergy diagnostics with the epicutaneous test is threatened with extinction. dermatologist 63: 250-25
  9. Trautmann A, Klein-Tebbe J (2013) Allergology in clinic and practice. Georg Thieme Publisher Stuttgart S 186-245

  10. Treudler R (2010) Allergic diseases in pregnant women. dermatologist 61: 1027-1033
  11. Villarama CD et al (2004) Correlations of patch test reactivity and the repeated open application test (ROAT)/provocative use test (PUT). Food Chem Toxicol 42: 1719-1725
  12. Worm M et al (2007) Patch testing in children--recommendations of the German Contact Dermatitis Research Group (DKG). J Dtsch Dermatol Ges 5: 107-109
  13. Wohrl S et al (2003) Patch testing in children, adults, and the elderly: influence of age and sex on sensitization patterns. Pediatric dermatol 20: 119-123

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Last updated on: 29.10.2020