DermNet provides Google Translate, a free machine translation service. Note that this may not provide an exact translation in all languages


Baseline series of patch test allergens

Last reviewed: October 2023

Author(s): Dr Amanda Oakley, Waikato Hospital, Hamilton New Zealand, 2008; updated by Dr Geetika Seth, Dermatopathology fellow, Boston University, Chobanian and Avedisian School of Medicine, Boston, USA; Dr Sabrina Sapsford, Dermatology Research Fellow, Te Whatu Ora, Counties Manukau, NZ; and Dr Libby Whittaker, DermNet Medical Writer, NZ (2023)

Reviewing dermatologist: Dr Ian Coulson

Edited by the DermNet content department


What is a baseline series of patch test allergens?

Patch tests are used to identify the cause of allergic contact dermatitis. Standard or baseline series of allergens are recommended for people undergoing patch testing because these include the most common and important allergens that cause dermatitis, and will identify over 70% of culprit allergens. Specific allergens may be added or removed from the series as they become more or less frequent culprits.

Additional allergens may also be tested depending on the patient’s medical and social history, the site of their suspected contact dermatitis or occupation.

The specific standard/baseline series may vary by geographical location due to differences in allergens, medicaments and social practices. The European Baseline Series (EBS) is most commonly used in Europe and elsewhere in the world. Other series include the International Standard, North American Baseline, and American Core Allergen; and series specific to other countries such as Belgium, Finland, Sweden, Hungary, Italy, Korea, Australia, and New Zealand.

The Paediatric Baseline Series has also recently been developed to aid the investigation of allergic contact dermatitis in children.

How are the patch tests prepared?

The patch test centre usually orders its allergens from several manufacturers. Most chemicals are mixed in petrolatum and supplied in a syringe. A few chemicals are dissolved in water and 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 tested to determine the most suitable concentration for testing. If too weak, some people who are allergic to the chemical will not react to the test substance (false negative). If too strong, some people who are not allergic to the chemical will have an irritant reaction (false positive).

A small amount of each 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 patch test panels each with 10-12 allergens applied are fixed to the skin of the upper back. 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, usually 48 hours later.

Pre-prepared patch test allergens

The Thin-layer Rapid-Use Epicutaneous (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.


Which chemicals are included in the baseline series?

The chemicals in the baseline series depend on which series is being used. The European Baseline Series (updated 2023) is described below. Most test substances are single compounds but some of the tests are mixtures of closely-related chemicals.

European Baseline Series

The European Baseline Series (EBS) includes 32 allergens (see table below), with another 10 in the extended series (including linalool and limonene hydroperoxides, compositae mix II, diazolidinyl urea, 2-bromo-2-nitropropane-1,3-diol, 2-n-octyl-4-isothiazolin-3-one, sorbitan sesquioleate, and sorbitan monooleate).

European Standard of patch test allergens

Allergen Concentration % (w/w), in petrolatum (unless stated otherwise) Source of dermatitis Positive reaction
Potassium dichromate 0.5 Chrome (cement, shoes, metal) Positive patch test to potassium dichromate
p-Phenylenediamine (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
Caine mix III 10.0 Benzocaine (local anaesthetic) Positive patch test to benzocaine
Nickel sulfate 5.0 Nickel (metal, coins, jewellery) Positive patch test to nickel
2-hydroxyethyl methacrylate (HEMA) 2.0 Adhesives, nail products, dental and orthopaedic materials, UV inks  
Colophonium 20.0 Rosin and colophony (adhesive) Positive patch test to rosin
Paraben mix 16.0 Parabens (preservative) Positive patch test to parabens
N-Isopropyl-N-phenyl-4-phenylenediamine (IPPD) 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
2-mercaptobenzothiazole (MBT) 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 I (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
Sodium metabisulfite 1.0 Preservative in foods, pharmaceuticals, and other products  
Propolis 10 Resinous mixture produced by bees, used in a variety of both oral and topical agents, cosmetics, and mouthwashes  
Cl+Me-isothiazolinone (Kathon) / methylchloroisothiazolinone + methylisothiazolinone (MCI/MI) 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
Fragrance mix II (lyral, citral, farnesol, citronellol, hexyl cinnamic aldehyde, coumarin) 14  Fragrance and perfume  fragrance patch sm
Hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral) 5.0 Fragrance ingredient used in perfumes, soaps, cosmetics  
Methylisothiazolinone 0.2 in water Preservative  methylisothiazolinone patch sm
Benzisothiazolinone 0.1 Industrial preservative used in inks, paints, varnishes, adhesives, cleaning products, and cooling fluids  
Textile dye mix  6.6 Disperse textile dyes  disperse orange patch sm
Decyl glucoside 5.0 Surfactant found in many cleansers and cleaning products  

T.R.U.E.® Test series

Compared to the European Baseline Series, at the time of writing the T.R.U.E.® Test allergens do not include 2-hydroxyethyl methacrylate, IPPD, sesquiterpene lactone mix, sodium metabisulfite, propolis, fragrance mix II, Lyral, methylisothiazolinone, benzisothiazolinone, textile dye mix, or decyl glucoside. The three test panels comprise 35 allergens, including the following:

Allergen Concentration mg/cm2 in stated vehicle Source of dermatitis Positive reaction
Carba mix 0.25 in hydroxypropyl cellulose Rubber antioxidant Positive patch test to carba mix
Ethylenediamine dihydrochloride 0.05 in methyl-cellulose Ethylenediamine (preservative) Positive patch test to ethylenediamine
Thiomersal 0.007 in hydroxypropyl cellulose Thiomersal (mercurial preservative) Positive patch test to thiomersal
Diazolidinyl urea 0.55 in povidone Formaldehyde-releasing preservative Positive patch test to diazolidinyl urea
Imidazolidinyl urea 0.60 in povidone Imidazolidinyl urea (preservative) Positive patch test to imidazolidinyl urea
Hydrocortisone-17-butyrate 0.02 in povidone Topical corticosteroid hydrocortisone butyrate patch sm
2-Bromo-2-nitropropane-l,3-diol (Bronopol) 0.25 in povidone Formaldehyde-releasing preservative Positive patch test to bronopol
Bacitracin 0.6 in hydroxypropyl cellulose Antibiotic (topical medication)  bacitracin patch sm2
Disperse Blue 106 0.05 in povidone Textile dye  disperse blue patch sm
Parthenolide (feverfew) 0.003 in povidone Compositae plant Positive patch test to feverfew
Gold sodium thiosulphate 0.075 in hydroxypropyl cellulose Metal see Gold Positive patch test to sodium thiosulfate (gold)
Quaternium-15 (Dowicil 200) 1.0 in hydroxypropyl cellulose Quaternium-15 (preservative) Positive patch test to quaternium 15
Black rubber mix 0.075 in povidone Rubber products (eg, tires, sporting equipment, goggles, shoes)  
Quinoline mix (including clioquinol) 0.19 in povidone Antibiotics  

North American Baseline Series

The North American Contact Dermatitis Group (NACDG) Baseline Series includes a greater range of allergens (50 baseline allergens, or extended versions with 65 or 80 allergens). It does not include thiomersal. Some of the other 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
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 5.0 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 0.1 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 II 5.0 Tanacetum vulgare (ragweed), Arnica montana (arnica), Parthenolide (feverfew), Chamomilla romana (chamomile), Achillea millefolium (yarrow) Positive patch test
Cocamidopropylbetaine 1.0 in water Surfactant, detergent  
Amerchol L-101 5.0 Lanolin  
Cinnamal 1.0 Fragrance, cinnamon, spices  

American Core Series

A core allergen series with 80 allergens was released by the American Contact Dermatitis Society (ACDS) in 2013, with subsequent updates in 2017 and 2020. Currently there are 90 allergens listed, available in 9 panels. These are intended to be used as a way to logically extend testing for patients beyond the T.R.U.E.® Test, scaling testing up or down depending on the patient and context. More recent additions in 2020 include:

Allergen Concentration (%) in petrolatum (unless stated otherwise) Source of dermatitis
Peppermint oil


Essential oil
Jasmine absolute oil


Essential oil

20.0 in alcohol

Resin used as food glaze, furniture sealant, and in cosmetics


Food additive, colouring agent
Lauryl polyglucose (ie, lauryl glucoside)


Surfactant used in products such as shampoo, cosmetics, sunscreens, and deodorants
Benzyl salicylate



International Standard Series

In comparison to the European Baseline Series, the International Standard Series (with 30 allergens) from the International Contact Dermatitis Research Group (ICDRG) does not contain caine mix, sodium metabisulfite, and benzisothiazolinone. The 0.2% methylisothiazolinone (MI) test and 0.01–0.02% methylchloroisothiazolinone + methylisothiazolinone (MCI/MI) tests have been replaced by a single 0.215% MCI/MI test, following a study (Isaksson et al, 2021) showing the 0.215% mix was superior in detecting patients with MCI/MI contact allergy than the other tests combined.

The expanded International Comprehensive Series contains 80 allergens.

The New Zealand Baseline Series

In 2020, patch testing practice in New Zealand was reviewed and the need for national surveillance and identification of relevant allergens was identified. In 2021, the New Zealand Baseline Series (NZBS) was developed by a national panel of dermatologists using a large body of retrospective data. This is the most up-to-date series for the New Zealand population.

There are 30 allergens in the NZBS and another 30 in the extended series, including many from the EBS and the NACDG Baseline Series. Other allergens include:

Allergen Concentration (%) and vehicle (petrolatum unless stated otherwise) Source of dermatitis
Hydroperoxides of linalool 1.0

Fragrance ingredient

Tea tree oil oxidised 5.0

Essential oil

Benzalkonium chloride 0.1 in water

Antiseptics, cleaning products

Hydroperoxides of limonene 0.3

Fragrance ingredient

Paediatric Baseline Series

Patch testing in the paediatric population has been less extensively studied than in the adult population.

In 2017, the US Food and Drug Administration (FDA) approved the T.R.U.E.® Test for use in children aged 6 to 17.

More recently, the Paediatric Baseline Series (PBS) was published in 2018 based on expert consensus at the American Contact Dermatitis Society meeting. The PBS includes 38 allergens, with 2 blank ‘what else’ spots for other allergens as appropriate. It has been found to be superior in picking up positive patch test results than the T.R.U.E.® Test, which unlike the PBS does not include the following important contact allergens in children:

An Australian Paediatric Baseline Series was also subsequently proposed in 2020.

What about other allergens?

There are numerous other chemicals that have been reported to cause contact allergy occasionally. About 15% of patients who 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 based on history taking and potential exposures.

Several series have been developed for patients who present with dermatitis on specific sites of the body or for those with certain occupations (eg, Hairdressing Series, Dental Screening) or other risk factors (eg, Shoe or 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 allergen or house dust mite.

Sometimes patients may be strongly positive to an allergen with which, according to their medical and social history, they have little or no contact. In this case, consort contact allergic dermatitis may also be considered.



  • Chemotechnique Diagnostics. New EBS 2023 Comparison with TRUE Test®. The Patch Tester. March 2023;14:4–7. PDF
  • Chemotechnique Diagnostics. Patch Test Products and Reference Manual. 2023. PDF
  • Dupuy E, Miller M, Harter N. What We Have Learned-Milestones in Pediatric Contact Dermatitis. Curr Dermatol Rep. 2022;11(1):1–12. doi: 10.1007/s13671-022-00353-w. Article
  • Felmingham C, Davenport R, Bala H. Allergic contact dermatitis in children and proposal for an Australian Paediatric Baseline Series. Australas J Dermatol. 2020 Feb;61(1):33–38. doi: 10.1111/ajd.13169. Journal
    Isaksson M, Anderson KE, Elsner P, et al. Patch Testing With Methylchloroisothiazolinone/Methylisothiazolinone Using a New Diagnostic Mix-A Multicenter Study From the International Contact Dermatitis Research Group. Dermatitis. 2021;32(4):220–224. doi: 10.1097/DER.0000000000000657. Journal
  • Sapsford S, Cheng H, Judd L. Patch testing in New Zealand: barriers to evidence-based care. Australas J Dermatol. 2021;62(1):47–50. doi: 10.1111/ajd.13449. Journal
  • Seine AJ, Baird EA, Chan L, et al. A baseline patch test series for New Zealand. Australas J Dermatol. 2021;62(4):489–495. doi: 10.1111/ajd.13673. Journal
  • Schalock PC, Dunnick CA, Nedorost S, et al. American Contact Dermatitis Society Core Allergen Series. Dermatitis. 2013;24(1):7–9. doi: 10.1097/DER.0b013e318281d87b. Journal
    Schalock PC, Dunnick CA, Nedorost S, et al. American Contact Dermatitis Society Core Allergen Series: 2020 Update. 2020 Sep-Oct;31(5):279-282. doi: 10.1097/DER.0000000000000621. Journal
  • SmartPractice. AllergEAZE: 2021/2022 Allergen Catalogue. 2022. PDF
  • Tennstedt D. Patch tests: indications or when testing should be performed? Ann Dermatol Venereol. 2009;136(8-9):579–583. doi: 10.1016/j.annder.2009.06.012. Journal
  • T.R.U.E. Test® Reference Manual. SmartPractice; 2018. Accessed August 30, 2023. PDF
  • Wilkinson SM, Gonçalo M, Aerts O, et al. The European baseline series and recommended additions: 2023. 2023 Feb;88(2):87–92. doi: 10.1111/cod.14255. Journal
  • Yu J, Atwater AR, Brod B, et al. Pediatric Baseline Patch Test Series: Pediatric Contact Dermatitis Workgroup. 2018 Jul/Aug;29(4):206–212. doi: 10.1097/DER.0000000000000385. Journal

On DermNet

Other websites

Books about skin diseases


Related information

Sign up to the newsletter