Explanation of table 1

Table 1 provides an alphabetical listing of about 4900 individual chemicals and other compounds (including 550 'new' chemicals, not mentioned in the previous edition) and approximately 2300 synonyms, for which concentrations and vehicles for patch testing have been documented. The table has 6 vertical columns, which contain the following information:

  1. Name of the chemical
  2. Synonyms/other names
  3. Patch test concentrations & vehicles, and reference numbers
  4. Merck Index Online number
  5. Personal Care Products Council On-Line INFOBASE monograph
  6. Comments

Column 1: Name of the chemical

This column lists all chemicals, both 'preferred names' and 'synonyms/other names' alphabetically. 'Preferred names' begin with a capital letter. 'Other names/synonyms' are not capitalized, unless they are (registered or unregistered) brand names (recognizable by ®; not verified whether they are correct and still in use), abbreviations, official plant names or they begin with the name of a country, city, or a proper name. The choice of the 'preferred name' for a chemical has (with, for practical purposes, some exceptions) been standardized according to the following general rules:

  • INCI names are (virtually) always the preferred names
  • chemicals (RIFM fragrance materials excepted) which are monographed in the Merck Index online database have their Merck Index designation as 'preferred name' (although it does not always seem to be a logical choice)
  • fragrance materials investigated by the Research Institute for Fragrance Materials (RIFM) have their RIFM names as 'preferred names', unless they are mentioned in the INCI system (which is nearly always only the European CosIng INCI nomenclature)
  • colors are mentioned by their INCI name or, if not included in the INCI system, have their 'common name' or 'color index name' as 'preferred name' (not standardized)
  • for all other chemicals the 'preferred name' is usually the name used in the publications where information was derived from; however, if the chemical, while searching for its CAS number, would come up more frequently as a synonym of this chemical, the synonymous name was used as main entry.

Column 2: Synonyms/other names

This column may list one or more synonyms when the corresponding chemical in column 1 is a 'preferred name', or refers to the 'preferred name' when the corresponding chemical in Column 1 is a synonym ('see....').

Column 3: Patch test concentrations & vehicles, and reference numbers

This column provides for each chemical ('preferred name') in Column 1 concentrations and vehicles for patch testing as shown in textbooks (1,2,5,6,7,8,9,10,15,18,22,23) and other sources (mostly articles in 'Contact Dermatitis', the ‘American Journal of Contact Dermatitis’, and 'Dermatitis'). The concentrations and vehicles derived from references 4, 11,12,14,960 and 961 are not recommended test concentrations, but such that did not cause irritation after a 48 hour closed patch test in a panel of volunteers or in Repeated Insult Patch Tests performed by RIFM, unless otherwise mentioned (e.g., 'slight irritation in 3/20 subjects'). Such data are marked with the designation 'see Note A', 'see Note C' or 'see Note D' (explanation given below). The concentrations given in ref 76 are those used in cosmetic allergy ingredient patch testing in The Netherlands (indicated by 'see Note B', explained below).

The abbreviations used for the vehicles are as follows:

  • acet = acetone
  • alc = alcohol
  • bl = butyrolactone
  • chlorof = chloroform
  • co = castor oil
  • comm prep = commercial preparation
  • dep = diethyl phthalate
  • DMSO = dimethyl sulfoxide
  • epi = 45% alcohol, 10% propylene glycol, 45% isopropyl alcohol
  • ethyl acet = ethyl acetate
  • euc anh = eucerinum anhydricum
  • glyc = glycerin
  • isopr alc = isopropyl alcohol
  • isopr palm = isopropyl palmitate
  • MEK = methyl ethyl ketone
  • mo = mineral oil
  • ol arach = oleum arachidis
  • oo = olive oil
  • paraff liq = paraffinum liquidum
  • peg = polyethylene glycol
  • pet = petrolatum
  • prop glyc = propylene glycol
  • sat sol = saturated solution
  • sol = solution

Column 4: Merck Index number

A number in this column indicates that the corresponding chemical in Column 1 is monographed in the Merck Index Online database (www.rsc.org/merck-index, accessible on subscription only), the number corresponding to the chemical's Merck Index monograph number.

Column 5: Personal Care Products Council On-Line INFOBASE monograph

A '+' in this column means that the corresponding chemical in Column 1 is monographed in the Personal Care Products Council On-Line INFOBASE.

Column 6: Comments

This columns begins with the CAS (Chemical Abstracts Service) number(s) of the chemical. These have not been verified by the CAS organization and some may therefore be erroneous (which also seems to apply to the major chemical databases). The CAS numbers have largely been obtained from the chemical databases mentioned above. In the case of chemicals having an INCI name, CosIng (EU) and the Personal Care Products Council On-Line INFOBASE (USA) were consulted and the CAS numbers mentioned there used.

The column also contains a variety of other information, all of which relates more or less directly to patch testing procedures (e.g. 'test concentration may be irritant', '20 controls were negative', 'no controls mentioned', 'risk of patch test sensitization' etc.), When a chemical has caused photosensitivity, immediate contact reactions (contact urticaria) or patch test sensitization, relevant information and references are given under this heading.

A complete list of chemicals which have caused photosensitivity is provided in Table 5, of chemicals which have caused immediate contact reactions (contact urticaria) is provided in Table 6, and of chemicals which have caused, or are at risk of causing, patch test sensitization is provided in Table 7. Sometimes in the column 'Comments' it may read: 'see Note A', 'see Note B', 'see Note C', or 'see Note D'. These notes have the following meaning:

Note A References 4,11,12 and 14 relate to fragrance materials tested by the Research Institute for Fragrance Materials (RIFM). The irritant properties of each fragrance material have been evaluated by a 48-hour closed patch test on a panel of human subjects (up to 50, usually between 20 and 30). Thus, the concentration and vehicle (which is almost always petrolatum) mentioned in column 3 is not a test advice from RIFM or the author, but a test concentration which did not induce irritation after a 48-hour closed patch test (unless otherwise indicated). This concentration may consequently be (reasonably) safe for patch testing, as far as irritation is concerned.

Note B These are cosmetic ingredients, which have been tested on patients with suspected cosmetic dermatitis in two studies. In the first study, performed between 1985 and 1993, the members of the Dutch Contact Dermatitis Group and several non-member dermatologists interested and experienced in contact dermatitis have tested patients suspected of allergic cosmetic dermatitis with all ingredients of cosmetic products reacting upon patch testing. The ingredients were prepared for patch testing by the Cosmetics Division of the Dutch Food Inspection Service (former Head: J. Willem Weijland, PhD). The test concentrations and vehicles for ingredients for which there were no published patch testing data were advised by Dr. Weijland and the author, based on their experience and the chemical nature of the ingredients ('educated guess').

In the second study, performed between 2010 and 2018, dermatologists participating in CESES, a Dutch surveillance system investigating the safety of cosmetic products, tested patients reacting to a cosmetic product, as in the first study, with the ingredients of the culprit product. The ingredients were obtained from the producers and the test concentrations of chemicals for which no test data were available were advised by the current Head of the Netherlands Food and Consumer Product Safety Authority, C.E. (Diny) Hissink, PhD (who also supplied the test materials) and the author of this book.

Thus, test concentrations mentioned in column 3 and referring to reference 76 have been patch tested in 1-10 patients (but very often in only 1 or 2) suffering from or suspected to suffer from contact allergy to cosmetic products. No irritant reactions were observed to the test material. As a consequence, these test concentrations and vehicles should not be regarded as our 'test advice', but rather should give the investigator some direction in deciding what concentration/vehicle to choose for this particular chemical.

Note C These chemicals are fragrances that have been investigated by the Research Institute for Fragrance Materials (RIFM), reviews of which have been published in Food and Chemical Toxicology between 2000 and 2013 (ref. 960). The irritant properties of each fragrance material have been evaluated in the induction phase of a Repeated Insult Patch Test, where the chemical was applied to the skin (mostly the upper arm) of 20 to 50 volunteers for 24 hours. Induction applications were made to the same site on Monday, Wednesday and Friday for a total of 9 applications during a 3-week period and the skin was examined for signs of irritancy. In most cases, no irritant reactions were observed. The concentration of the chemical and the vehicle used for application are mentioned in column 3 of table 1. These are, therefore, not a test advice from RIFM or the author, but a test concentration which did not induce irritation in the induction phase of a Repeated Insult Patch Test (9x 24 h application in 3 weeks).This concentration may consequently be (reasonably) safe for patch testing, as far as irritation is concerned (960).

Note D These chemicals are fragrances that have been investigated by the Research Institute for Fragrance Materials (RIFM), reviews of which have been published in Food and Chemical Toxicology between 2000 and 2013 (ref. 961). The irritant properties of each fragrance material have been evaluated by a 48-hour closed patch test on a panel of human subjects (up to 50, usually between 20 and 30). Thus, the concentration and vehicle (which is almost always petrolatum) mentioned in column 3 is not a test advice from RIFM or the author, but a test concentration which did not induce irritation after a 48-hour closed patch test. This concentration may consequently be (reasonably) safe for patch testing, as far as irritation is concerned (961).

Test advice

The column 'Comments' also provides - for a very small number of chemicals - the author's advice for test concentration and vehicle. Such test advice (on the basis of assessment of literature data) is, with a few exceptions, given only then when Column 3 'Patch test concentrations & vehicles and reference numbers' has two or more test recommendations, which differ considerably, either in concentration or in the nature of the vehicle for testing. We have not always given test advice where more recommendations were provided, because there is usually little sound evidence for what would be the 'right' concentration and vehicle. As many of these recommendations were made by experienced and authoritative investigators, it would be somewhat presumptuous to select one, except when data from literature or personal experience would support such a choice.

Nevertheless, in the vast majority of cases, the reader will find little difficulty in choosing a concentration and vehicle for patch testing, on the basis of the data provided in this book.

Commercially available allergens

These are indicated with 'Chemo', 'SPCan' and 'SPEur':

Chemo: Chemotechnique Diagnostics, www.chemotechnique.se

SPCan: SmartPractice CANADA, www.smartpracticecanada.com

SPEur: SmartPractice EUROPE, www.smartpracticeeurope.com

If only one concentration and vehicle is mentioned in column 3 and the commercial allergen has the same concentration and vehicle, only the company names providing the allergen are mentioned, e.g. 'Chemo, SPCan'. In all other situations, the test concentrations and vehicles of the commercial allergens are specified after the company's name, e.g., 'Chemo (0.1% aqua)'.