True cross-sensitization, false cross-sensitization and otherwise

Epicutaneous Patch Testing in Type IV Allergy Diagnostics: State of the Art and Best Practice Recommendations

This chapter summarises all relevant aspects of patch testing, closely following recommendations outlined in a recent European, and a German S3 guideline on diagnostic patch testing with contact allergens and medicinal products (drugs). Patch testing is indicated in patients suspected of suffering, or having been suffering, from delayed-type hypersensitivity leading to allergic contact dermatitis or other skin and mucosal diseases. Sections of this chapter include detailed indications, reasons for possibly postponing the test, considerations on choosing haptens (contact allergens) to test, various aspects of the application of patch test allergen preparations (storage, dosing) and of testing with individual materials provided by the patients. Special aspects of patch testing in cutaneous adverse drug reactions, children, or occupational contact dermatitis are outlined. Supplemental test methods, notably the repeated open application test, are briefly described. Finally, the final evaluation in terms of assessment of clinical relevance of reactions and patient counselling are outlined.

Sensitizing Capacities and Cross-Reactivity Patterns of Some Diisocyanates and Amines Using the Guinea-Pig Maximization Test. Can p-phenylenediamine be Used as a Marker for Diisocyanate Contact Allergy?

Background:

Isocyanates are mainly considered respiratory allergens but can also cause contact allergy. Diphenylmethane-4,4′-diamine (4,4′-MDA) has been considered a marker for diphenylmethane-4,4′-diisocyanate (4,4′-MDI) contact allergy. Furthermore, overrepresentation of positive patch-test reactions top-phenylenediamine (PPD) in 4,4′-MDA positive patients have been reported.

Objectives:

To investigate the sensitizing capacities of toluene-2,4-diisocyanate (2,4-TDI) and PPD and the cross-reactivity of 4,4′-MDA, 2,4-TDI, dicyclohexylmethane-4,4′-diamine (4,4′-DMDA), dicyclohexylmethane-4,4′-diisocyanate (4,4′-DMDI), 4,4′-MDI and PPD.

Methods:

The Guinea Pig Maximization Test (GPMT) was used.

Results:

PPD was shown to be a strong sensitizer (p<0.001). Animals sensitized to PPD showed cross-reactivity to 4,4′-MDA (p<0.001). Animals sensitized to 4,4′-MDA did not show cross-reactivity to PPD. 8 animals sensitized to 2,4-TDI were sacrificed due to toxic reactions at the induction site and could thus not be fully evaluated.

Conclusion:

PPD was shown to be a strong sensitizer. However, it cannot be used as a marker for isocyanate contact allergy. On the other hand, positive reactions to 4,4′-MDA could indicate a PPD allergy. The intradermal induction concentration of 2,4-TDI (0.70% w/v) can induce strong local toxic reactions in guinea-pigs and should be lowered.

Sensitization and cross-reactivity patterns of contact allergy to diisocyanates and corresponding amines: investigation of diphenylmethane-4,4'-diisocyanate, diphenylmethane-4,4'-diamine, dicyclohexylmethane-4,4'-diisocyanate, and dicylohexylmethane-4,4'-diamine

Background

Isocyanates are used in polyurethane production. Dermal exposure to isocyanates can induce contact allergy. The most common isocyanate is diphenylmethane diisocyanate used for industrial purposes. The isomer diphenylmethane‐4,4′‐diisocyanate (4,4′‐MDI) is used in patch testing. Diphenylmethane‐4,4′‐diamine (4,4′‐MDA) is its corresponding amine. Concurrent reactions to 4,4′‐MDI and 4,4′‐MDA have been reported, as have concurrent reactions to 4,4′‐MDI and dicyclohexylmethane‐4,4′‐diisocyanate (4,4′‐DMDI).

Objectives

To investigate the sensitization capacities and the cross‐reactivity of 4,4′‐MDI, 4,4′‐MDA, 4,4′‐DMDI, and dicyclohexylmethane‐4,4′‐diamine (4,4′‐DMDA).

Methods

The guinea‐pig maximization test (GPMT) was used.

Results

The GPMT showed sensitizing capacities for all investigated substances: 4,4′‐MDI, 4,4′‐MDA, 4,4′‐DMDI, and 4,4′‐DMDA (all p < 0.001). 4,4′‐MDI‐sensitized animals showed cross‐reactivity to 4,4′‐MDA (p < 0.001) and 4,4′‐DMDI (all p < 0.05). 4,4′‐MDA‐sensitized animals showed cross‐reactivity to 4,4′‐DMDA (p = 0.008).

Conclusion

All of the investigated substances were shown to be strong sensitizers. Animals sensitized to 4,4′‐MDI showed cross‐reactivity to 4,4′‐MDA and 4,4′‐DMDI, supporting previous findings in the literature. The aromatic amine 4,4′‐MDA showed cross‐reactivity to the aliphatic amine 4,4′‐DMDA.

Two decades of p-phenylenediamine and toluene-2,5-diamine patch testing - focus on co-sensitizations in the European baseline series and cross-reactions with chemically related substances

BACKGROUND

Cross-reactions and co-sensitizations are of great importance in understanding contact allergy and exposure sources.

OBJECTIVES

To investigate common cross-reactions and co-sensitizations in p-phenylenediamine (PPD)-sensitized and toluene-2,5-diamine (TDA)-sensitized individuals.

METHODS

From our patch test population, 8036 patients patch tested with the European baseline series were extracted. Readings had to be performed at least on day 3 according to ICDRG guidelines.

RESULTS

Two hundred and fifty-one patients were sensitized to PPD and/or TDA; 231 patients were sensitized to PPD, and 109 to TDA. Significant differences were observed regarding the strengths of patch test reactions to PPD and number of cross-reactions. For TDA, a difference was found between all reaction strengths, except between + and ++ strengths. PPD-sensitized individuals were more likely to be sensitized to carba mix, cobalt chloride, colophonium, p-tert-butyl phenolformaldehyde resin, paraben mix, and methylisothiazolinone. TDA-sensitized individuals were more often sensitized to carba mix.

CONCLUSIONS

Cross-reactivity was commonly found among individuals sensitized to PPD or TDA, and was strongly related to the strength of the patch test reaction. Regarding co-sensitizations, a frequently appearing or common exposure source could not be determined. However, modification of the allergen by, for example, the skin microbiota may have caused the formation of molecules that are, for the human immune system, indistinguishable from PPD.

A dynamic landscape of allergen associations in delayed-type cutaneous hypersensitivity

BACKGROUND

Delayed-type hypersensitivity represents a significant clinical and public health challenge. Patients undergoing patch testing may exhibit positive reactions to more than one allergen. It is recognized that reactions to specific pairs of allergens are associated, reflecting a combination of exposure patterns and structural similarity.

OBJECTIVES

To explore the influence of time of testing, age, sex and atopy status on allergen pair associations in a series of 45 110 consecutive patients tested over 30 years.

METHODS

Patch test records of all patients undergoing testing with a modified European baseline series between 1985 and 2014 were retrieved from a database at St John's Institute of Dermatology. Reactions were read on days 2 and 4. For each allergen it was recorded whether the allergen was tested and whether the result was positive or negative.

RESULTS

This is the largest reported study of patch test allergen pair relationships. Our analysis shows a high degree of variability in allergen pair associations. Rigorous statistical analysis reveals a large number of differences between groups, including a significant increase in the association between formaldehyde and multiple formaldehyde-releasing preservatives over the study period, in addition to pair associations with cobalt and formaldehyde-releasing preservatives. These were present to a significantly greater extent in men than in women.

CONCLUSIONS

These observations extend our understanding of cutaneous allergy, with implications for both clinical practice and mechanisms of cutaneous hypersensitivity.

In situ chemical behaviour of methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI) in reconstructed human epidermis: a new approach to the cross-reactivity issue

BACKGROUND

Methylisothiazolinone (MI) [with methylchloroisothiazolinone (MCI) in a ratio of 1:3, a well-recognized allergenic preservative] was released as an individual preservative in the 2000s for industrial products and in 2005 for cosmetics. The high level of exposure to MI since then has provoked an epidemic of contact allergy to MI, and an increase in MI/MCI allergy. There are questions concerning the MI/MCI cross-reaction pattern.

OBJECTIVES

To bring a new perspective on the MI/MCI cross-reactivity issue by studying their in situ chemical behaviour in 3D reconstructed human epidermis (RHE).

METHODS

MI and MCI were synthesized with (13) C substitution at positions C-4/C-5 and C-5, respectively. Their in situ chemical behaviours in an RHE model were followed by use of the high-resolution magic angle spinning nuclear magnetic resonance technique.

RESULTS

MI was found to react exclusively with cysteine thiol residues, whereas MCI reacted with histidines and lysines. The reaction mechanisms were found to be different for MI and MCI, and the adducts formed had different molecular structures.

CONCLUSION

In RHE, different MI/MCI reactions towards different nucleophilic amino acids were observed, making it difficult to explain cross-reactivity between MI and MCI.

European Society of Contact Dermatitis guideline for diagnostic patch testing - recommendations on best practice

The present guideline summarizes all aspects of patch testing for the diagnosis of contact allergy in patients suspected of suffering, or having been suffering, from allergic contact dermatitis or other delayed-type hypersensitivity skin and mucosal conditions. Sections with brief descriptions and discussions of different pertinent topics are followed by a highlighted short practical recommendation. Topics comprise, after an introduction with important definitions, materials, technique, modifications of epicutaneous testing, individual factors influencing the patch test outcome or necessitating special considerations, children, patients with occupational contact dermatitis and drug eruptions as special groups, patch testing of materials brought in by the patient, adverse effects of patch testing, and the final evaluation and patient counselling based on this judgement. Finally, short reference is made to aspects of (continuing) medical education and to electronic collection of data for epidemiological surveillance.

Parthenium the terminator: An update

Parthenium dermatitis is a distressing dermatitis caused by the air borne allergen of the Compositae weed Parthenium hysterophorus. Uncommon presentations, newer insights in pathogenesis and management of this "scourge" are discussed in this article.

Analysis of para-phenylenediamine allergic patients in relation to strength of patch test reaction

BACKGROUND

Despite having a positive patch test reaction to para-phenylenediamine (PPD), some patients continue to dye their hair, while others are forced to give up or abandon this practice. This difference in patient behaviour could be due to the degree of sensitization.

OBJECTIVES

To establish whether the ability to continue dyeing hair in PPD allergic patients is related to the strength of patch test reaction. To note differences in other clinical features in relation to the strength of patch test reaction.

METHODS

We analysed retrospectively the patch test records of 400 sequential PPD-positive patients for the strength of patch test reaction (+, ++, +++) and different clinical features. Data were analysed using Cochran-Mantel-Haenszel chi2 tests.

RESULTS

There was a strong linear relationship between the strength of patch test reaction and continuation with hair dyeing. Patients were more likely to report a history of hair dye reaction with increasing strength of patch test reaction. There was no difference in strength of patch test reaction in relation to age, site of rash, occupation (hairdressing) or history of atopic eczema. Overall concomitant reactivity with related aromatic amine allergens (benzocaine, N-isopropyl-N-phenyl-para-phenylenediamine, para-aminobenzoic acid) was infrequent.

CONCLUSIONS

Patients with stronger patch test reactions (++, +++) are more likely to have a clear history of reacting to hair dye and are less likely to still be dyeing their hair.

A multifactorial analysis of concurrent patch-test reactions to nickel, cobalt, and chromate

BACKGROUND

Previous research indicates that positive patch tests to nickel (II) sulphate, cobalt (II) chloride and potassium dichromate commonly occur together.

METHODS

To further examine the relationship between nickel, cobalt, chromate, and the factors that may potentially be related to concurrent sensitizations to two or all three metal allergens, data from the Information Network of Dermatology Departments have been investigated.

RESULTS

Women had a higher conditional odds of concurrent nickel-cobalt (OR = 6.80; 95% CI: 5.65-8.19) and nickel-chromate (OR = 2.13; 95% CI: 1.67-2.72) reactions than men. Construction workers had a significantly higher odds of cobalt-chromate reactions (OR = 13.89; 95% CI: 10.36-18.64), while the odds of isolated cobalt allergy was only 0.92 (95% CI: 0.48-1.74). Patients with underlying atopic eczema/dermatitis syndrome had a 40-90% higher chance of any positive outcome, which involved chromate. Polysensitization, defined as the number of positive reactions to standard series substances other than nickel, cobalt, and chromate, was also significantly associated with the concurrent reactions; moreover, steady and significant effect gradients were noted.

CONCLUSIONS

This research confirms the occupational nature of cobalt-chromate concurrent reactions, in particular, in construction workers. Polysensitization, which is considered to represent susceptibility to delayed-hypersensitivity in general, is also associated with the concurrent reactions to the metals. Hence, not only coupled exposure, but also individual susceptibility may be responsible for concurrent reactions to metals in man.

The value and limitations of rechallenge in the guinea pig maximization test

The guinea pig maximization test (GPMT) has played a primary rôle in the evaluation of potential skin contact sensitizers for 25 years. In the OECD Guideline 406 from 1993, it is specifically suggested that equivocal results from the initial challenge in the GPMT should be evaluated further with a repeated challenge. However, there exist few published rechallenge data and the guideline does not describe how rechallenge data should be interpreted. In this paper, we have used examples from published results to illustrate both the positive value and the limitations of repeated challenges, including cross challenge. Testing with modified concentrations may also help to indicate whether or not the response is allergic in nature, particularly where there has been a low level of skin reaction observed in shamtreated controls, or where a low level of skin reaction is the dominant response in the test animals. In conclusion, the data presented demonstrate that, as a tool for the investigation of skin sensitizing potential, the GPMT can benefit from an experienced scientific evaluation of rechallenge data, but that this information should not be treated in a mechanistic fashion.

The chemistry of contact allergy: why is a molecule allergenic?

This review concentrates on some specific aspects of the chemistry of allergic contact dermatitis. The way low molecular weight chemicals react with skin proteins to form complete antigens will be discussed and the development of molecular modelling techniques to analyse molecular recognition presented. Subsequently, how knowledge of the chemical structure can be used to estimate the allergenic activity of a molecule will be considered. This aspect includes work with qualitative and quantitative structure-activity relationships (SAR) in the field of contact allergy.

Pattern of cross-sensitivity between 4 Compositae plants, Parthenium hysterophorus, Xanthium strumarium, Helianthus annuus and Chrysanthemum coronarium, in Indian patients

To assess the pattern of cross-sensitivity between 4 members of the Compositae family, namely Parthenium hysterophorus L., Xanthium strumarium L., Helanthus annuus L. and Chrysanthemum coronarium L., 63 patients clinically diagnosed to have airborne contact dermatitis, and 51 controls having well-defined patterns of contact dermatitis caused by agents other than plants, were patch tested with measured amounts of standardized aqueous extracts of these plants. Positive reactions were obtained in 62 patients and 13 controls with Parthenium hysterophorus, in 47 patients and 9 controls with Xanthium strumarium, in 7 patients and 2 controls with Helianthus annuus, and in 13 of the 57 patients and one out of 28 controls tested with Chrysanthemum coronarium. 2 patients were allergic to all 4 of the plants; 14 patients to 3 plants, namely Parthenium, Xanthium and Chrysanthemum in 9 cases and Parthenium, Xanthium and Helianthus in 5 cases; 32 patients to 2 plants, namely Parthenium and Xanthium in 30 cases, and Parthenium and Chrysanthemum, and Xanthium and Chrysanthemum in 1 case each; 15 patients were allergic to 1 plant only, that being Parthenium. All the 47 patients allergic to Xanthium, 13 patients allergic to Chrysanthemum and 7 patients allergic to Helianthus were positive with some other plant as well. There was 1 patient who was allergic to Xanthium and Chrysanthemum but not to Parthenium. The titre of contact hypersensitivity (TCH) determined in the patients allergic to Parthenium, Xanthium and Helianthus showed values that varied widely with each plant in different patients, and there was no parallelism between the TCH with various plants.(ABSTRACT TRUNCATED AT 250 WORDS)

Compositae dermatitis in a Danish dermatology department in one year (I). Results of routine patch testing with the sesquiterpene lactone mix supplemented with aimed patch testing with extracts and sesquiterpene lactones of Compositae plants

To investigate the frequency of Compositae sensitivity, the recently-developed sesquiterpene lactone mix (SL mix) was included in the standard patch test series. Patients with positive reactions to this or patients suspected of having a Compositae allergy were supplementarily tested with a Compositae mix, consisting of ether extracts of 5 European Compositae plants. In the first year, 686 patients were tested with the SL mix and 79 with the Compositae mix. A total of 31 Compositae-sensitive patients (4.5%) were found. The frequency of positive reactions to either of the mixes was equal, but only 17 of 30 patients tested were positive to both mixes. Testing with the individual ingredients of the Compositae mix showed frequent positive patch test reactions to feverfew, followed in order by chamomile, tansy, yarrow and arnica. The reason for this distribution is discussed and the results of standard, photo- and other plant patch tests are presented. The only partial overlap between positive reactions to the mixes emphasizes the necessity of supplementary testing in patients suspected of Compositae allergy, as well as the lack of a reliable single screening agent. Since no cases of active sensitization or irritant reactions were seen, both the SL mix and the Compositae mix may be considered suitable for routine screening of Compositae allergy.

Allergic contact dermatitis caused by naturally occurring quinones

Quinones play a major role in allergic contact dermatitis caused by plants. The principal allergens are benzoquinones or naphthoquinones but also compounds, such as catechols and other phenolic or flavonoid compounds, which are bioconverted into ortho-quinones or para-quinones. The high electrophilic reactivity of these compounds toward nucleophilic residues of proteins associated with lipophilic properties may explain that they are strong sensitizers. The more important allergens are reported and their structure-activity relationship is discussed.

Occupational dermatoses from epoxy resin compounds

This study comprises 40 patients with skin disorders from current or previous occupational exposure to epoxy resin compounds (ERC) during 1984-1988. ERCs were the 3rd most common cause (32 of 264 cases: 12.1%) of currently relevant allergic contact dermatitis: 23 cases from epoxy resins based on the diglycidyl ether of bisphenol A (DGEBA-ERs), 5 from reactive diluents, 1 from amine hardeners (DETA), and 3 from epoxy acrylates. 2 cases (0.8%) of irritant contact dermatitis were due to ERCs. Methyl hexahydrophthalic anhydride (MHHPA, an epoxy hardener) caused 1 case of contact urticaria. Previously relevant occupational allergic contact dermatitis from DGEBA-ERs was detected in 5 cases. On patch testing, ERC allergens gave the following positive reactions: epoxy resin of the standard series in 35 cases (4.0% of 870 tested), epoxy reactive diluents in 10 (7.1% of 140), cycloaliphatic epoxy resins in 4 (11.1% of 36), epoxy acrylates in 4 (4.5% of 88), and amine compounds commonly used as epoxy hardeners in 17. Despite extensive patch test series, testing with patients' own ERCs remains important.

Cross-reaction in allergic contact dermatitis from alpha-methylene-gamma-butyrolactones: importance of the cis or trans ring junction

Cross-reaction in allergic contact dermatitis (ACD) is a highly stereoselective process. The importance of the cis or trans ring junction in alpha-methylene-gamma-butyrolactones in cross-reactivity was investigated by reacting Helenin (mostly a mixture of natural allergenic sesquiterpene lactones alantolactone 1 and isoalantolactone 2, which present a cis ring junction) in guinea pigs sensitized to model allergenic alpha-methylene-gamma-butyrolactones: cis-bicyclic lactone 3 and trans-bicyclic lactone 4.

Contact dermatitis to semisynthetic penicillins in factory workers

45 workers developed dermatitis after handling semi-synthetic penicillins in a factory. All reacted on patch test, but several agents had to be used. Only 7 reacted to benzyl penicillin. 1/3 reacted to only one allergen, while 2/3 reacted to several. The duration of exposure before symptoms was short, often less than 2 months. 19 had hay fever or asthma, and they developed their symptoms after a shorter exposure time. A survey for airborne antibiotics was performed.