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Baseline series of patch test allergens

Author: Dr Amanda Oakley, Waikato Hospital, Hamilton New Zealand, 2008.


What is a baseline series of patch test allergens?

Patch tests are used to identify the cause of contact allergic dermatitis. Standard or baseline series of allergens are recommended for use in everyone undergoing patch testing because these include the most common and important allergens that cause dermatitis.

The specific standard/baseline series may vary according to the locality of the patch testing centre. The European Standard Series is most commonly used in Europe and elsewhere in the world. Other series include International Standard, Belgium Standard, Finnish Standard, GIRDCA Series, Korean Standard, North American Series, North American Photopatch, Swedish Standard and Hungarian Standard.

How are the patch tests prepared?

The patch test centre may order its allergens from several manufacturers. Most chemicals are mixed in petrolatum and are supplied in a syringe. A few chemicals are dissolved in water and are supplied in a bottle. The patches consist of hypoallergenic adhesive paper with up to ten chambers. The chambers are made of metal or plastic and are round or square.

The chemicals have been carefully tested by the manufacturers and by dermatologists to determine the most suitable concentration for testing. If too weak, some people that are allergic to the chemical will not react to the test substance (false negative). If too strong, some people that are not allergic to the chemical will have a positive irritant reaction (false positive).

A small amount of a petrolatum-based allergen is carefully squeezed into a chamber. Liquid allergen solutions are dropped onto the filter paper placed in the test chamber. Two or three completed patches are fixed to the skin of the upper back; in some cases, an additional hypoallergenic tape may be necessary to keep them in place. Each patch is carefully numbered or labelled so the allergen in each chamber can be correctly identified.

The patches are generally left in place for 48 hours. The dermatologist will inspect the test site after they have been removed and at least once more, a couple of days later.

Preparing the Standard Series of patch test allergens

The T.R.U.E.® test series is already prepared; the backing paper is removed and the patches are carefully applied to the patient's back.

The T.R.U.E.® Series of patch test allergens

Which chemicals are included in the baseline series?

The chemicals in the baseline series depend on which one is being used. The European Baseline series used in 2006 is described below. Most test substances are single compounds but some of the tests are mixtures of closely-related chemicals.

European Standard Series

European Standard of patch test allergens

Allergen Concentration % (w/w) in petrolatum Source of dermatitis Positive reaction
Potassium dichromate 0.5 Chrome (cement, shoes, metal) Positive patch test to potassium dichromate
4-Phenylenediamine base (PPD) 1.0 Hair dye Positive patch test to PPD
Thiuram mix 1.0 Rubber antioxidant Positive patch test to thiuram mix
Neomycin sulfate 20.0 Neomycin (antibiotic) Positive patch test to neomycin
Cobalt chloride 1.0 Cobalt (metal) Positive patch test to cobalt
Benzocaine 5.0 Benzocaine (local anaesthetic) Positive patch test to benzocaine
Nickel sulfate 5.0 Nickel (metal, coins, jewellery) Positive patch test to nickel
Clioquinol (Chinoform and Vioform) 5.0 Clioquinol (antibacterial) Positive patch test to clioquinol
Colophonium 20.0 Rosin and colophony (adhesive) Positive patch test to rosin
Parabens mix 16.0 Parabens (preservative) Positive patch test to parabens
N-Isopropyl-N-phenyl-4-phenylenediamine 0.1 Rubber antioxidant, leather shoes, oils and greases Positive patch test to N-Isopropyl-N-phenyl-4-phenylenediamine
Lanolin alcohol 30.0 Wool fat Positive patch test to wool alcohols
Mercapto mix 2.0 Rubber antioxidant Positive patch test to mercapto mix
Epoxy resin 1.0 Epoxy resin (adhesive) Positive patch test to epoxy resin
Myroxylon pereirae resin 25.0 Balsam of Peru (fragrance) Positive patch test to balsam of Peru
4-tert-Butylphenol formaldehyde resin 1.0 Para-tertiary butyl phenol-formaldehyde resin (adhesive) Positive patch test to 4-tert-Butylphenol formaldehyde resin
Mercaptobenzothiazole 2.0 Rubber antioxidant Positive patch test to mercaptobenzothiazole
Formaldehyde 2.0 in water Formaldehyde and formalin (in clothing, cosmetics, household products) Positive patch test to formaldehyde
Fragrance mix (cinnamic alcohol, cinnamic aldehyde, hydroxycitronellal, amylcinnamaldehyde, geraniol, eugenol, isoeugenol, oakmoss absolute) 8.0 (Sorbitan sesquioleate 5% emulsifier) Fragrance and perfume Positive patch test to fragrance mix
Sesquiterpene lactone mix (alantolactone, dehydroxosus lactone, costunolide) 0.1 Compositae allergy (daisies) Positive patch test to sesquiterpene lactone mix
Quaternium-15 (Dowicil 200) 1.0 Quaternium-15 (preservative) Positive patch test to quaternium 15
Primin 0.01 Primula obconica (plant) Positive patch test to primin
Cl+Me-isothiazolinone (Kathon CG, 100 ppm) 0.02 in water Isothiazolinone (preservative) Positive patch test to isothiazolinone
Budesonide 0.01 Topical corticosteroid Positive patch test to budesonide
Tixocortol pivalate 0.1 Topical corticosteroid Positive patch test to tixocortal
Methyldibromo glutaronitrile 0.5 Formaldehyde-releasing preservative  methyldibromo glutaronitriie patch sm
Methylisothiazolinone 0.2 in water Preservative  methylisothiazolinone patch sm
Fragrance mix II  14  Fragrance and perfume  fragrance patch sm
Textile dye mix  6.6 Disperse textile dyes  disperse orange patch sm

T.R.U.E.® Test series

Compared to the European Standard Series, the T.R.U.E.® Test allergens do not include sesquiterpene lactone, primin or methyldibromo glutaronitrile. The test panels of 29 allergens include the following chemicals:

Allergen Concentration mg/cm2 in petrolatum Source of dermatitis Positive reaction
Carba mix 0.25 Rubber antioxidant Positive patch test to carba mix
Ethylenediamine dihydrochloride 0.050 Ethylenediamine (preservative) Positive patch test to ethylenediamine
Thiomersal 0.0070 Thiomersal (mercurial preservative) Positive patch test to thiomersal
Diazolidinyl urea 0.55 Formaldehyde-releasing preservative Positive patch test to diazolidinyl urea
Imidazolidinyl urea 0.60 Imidazolidinyl urea (preservative) Positive patch test to imidazolidinyl urea
Hydrocortisone-17-butyrate 0.02 Topical corticosteroid hydrocortisone butyrate patch sm
2-Bromo-2-nitropropane-l,3-diol (Bronopol) 0.5 Formaldehyde-releasing preservative Positive patch test to bronopol
Bacitracin 0.6 Antibiotic (topical medication)  bacitracin patch sm2
Disperse Blue 106/124 Mix 0.05 Textile dye  disperse blue patch sm
Parthelonid (feverfew) 0.003 Compositae plant Positive patch test to feverfew
Sodium thiosulfate (gold) 0.075 Metal see Gold Positive patch test to sodium thiosulfate (gold)

North American Standard Series

The North American Contact Dermatitis Group (NACDG) Standard Screening Tray includes a greater range of allergens. Unlike the European series, it does not include clioquinol or primin. Nor does it include thiomersal. Additional allergens in the NACDG series are shown below.

Allergen Concentration % (w/w) in petrolatum Source of dermatitis Positive reaction
DMDM Hydantoin 1.0 Formaldehyde-releasing preservative  
Bacitracin 20.0 Antibiotic  bacitracin patch sm
Mixed dialkyl thiourea 1.0 Rubber antioxidant, photographic fixing, resins, photocopy paper.  diethyl thiourea patch sm
Glutaraldehyde 0.5 A preservative used for sterilisation, embalming, tanning leather. Positive patch test
2-Bromo-2-nitropropane-l,3-diol (Bronopol) 0.5 Formaldehyde-releasing preservative  bronopol patch sm
Fragrance Mix II (lyral, citral, farnesol, citronellol, hyxyl cinnamic aldehyde, coumarin) 14.0 Fragrance and perfume Positive patch test
Propylene glycol 30.0 in water A vehicle in medications, cosmetics, foods.  
2-Hydroxy-4-methoxybenzophenone (Benzophenone 3) 10.0 Sunscreen Positive patch test to benzophenone 3
4-Chloro-3,5-xylenol (PCMX) 1.0 Preservative  
Ethyleneurea, melamine formaldehyde mix 0.1 Formaldehyde type of textile resin Positive patch test to melamine formaldehyde
Iodopropynyl butylcarbamate (Glycasil™) 0.2 Preservative for wood, paint, cooling fluids, cosmetics.  
Disperse Blue 106/124 Mix 1.0 Textile dye  disperse blue patch sm
Ethyl acrylate 0.3 An acrylic monomer used in adhesives and coatings Positive patch test
Glyceryl monothioglycolate (GMTG) 1.0 Acid perming solution Positive patch test to glyceryl monothioglycolate
Toluenesulfonamide formaldehyde resin 10.0 A synthetic resin in lacquers and adhesives (nail cosmetics)  TSF resin patch
Methyl methacrylate 2.0 Methacrylic monomer in plastics for dentures, artificial nails Positive patch test to methyl methacrylate
Compositae Mix 5.0 Tanacetum vulgare (ragweed), Arnica montana (arnica), Parthenolide (feverfew), Chamomilla romana (chamomile), Achillea millefolium (yarrow) Positive patch test
Dimethylol dihydroxyethyleneurea (Fix.CPN) 4.5 Formaldehyde type of textile resin  
Cocamidopropylbetaine 1.0 Surfactant, detergent  
Triamcinolone acetonide 5.0 Topical corticosteroid  

International Standard Series

In comparison to the European Standard Series, the International Standard Series (2001) does not contain cobalt, benzocaine, clioquinol, parabens, N-Isopropyl-N-phenyl-4-phenylenediamine, sesquiterpene lactone, primin or tixocortol. Imidazolidinyl urea is included. An extended series has been proposed.

What about other allergens?

There are numerous other chemicals that have been reported to cause contact allergy occasionally. About 15% of patients that have positive reactions at patch testing react to an allergen that is not in the baseline series. These allergens are detected using other series of allergens or individual standardised chemicals that have been selected by the dermatologist.

Several series have been developed for patients that present with dermatitis on specific sites of the body (e.g., 'face series', 'foot series'), and for those with certain occupations (eg, 'hairdressers series', dental series') or other risk factors ('shoe series', 'cosmetic series').

Atopy patch tests are sometimes undertaken in patients with atopic dermatitis where there is suspicion of exacerbation by a type 1 allergen such as a food or house dust mite.



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