Patch testing

This procedure is often suitable for testing nurses, physicians, pharmacists, and dentists who not infrequently develop contact sensitization following contact with various drugs, especially antibiotics, local anaesthetics, and antiseptic agents among others. 

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Sensitization results are based on a human maximization test (103) usiag a petrolatum vehicle. The effect is expressed as the number of paneHsts responding over the total number of paneHsts tested and was 0/25 except for spearmint (0/32). That is, at the dose iadicated, the oils werenot irritating when tested ia a 48-h closed patch test ia humans. 

Health and Safety Factors. Results of acute oral toxicity studies of 2-pyrrohdinone on white rats and guinea pigs show the LD q to be 6.5 ml,/kg. Skin patch tests on 200 human subjects indicate that 2-pyrrohdinone is a skin kritant, but there is no indication of sensitising action. It is a mild eye irritant (79). 

Skin Patch-Tested Repellents. SmaU areas of human forearms are marked and treated with smaU amounts of repeUent on a unit area basis to ensure that the treatment rate is always the same between subjects (7). The patches are tested at 0 and 4 hours against smaU numbers (ca 15) of mosquitoes. This method does not consider creep, movement of repeUent across the skin surface, or the iateraction between two chemicals owiag to such lateral movement of chemical. 

Hair colorants, the fourth class of color additives, may be used only to color scalp hair and may not be used in the area of the eye. Use of these colorants is exempt, that is, coal-tar hair dyes may be sold with cautionary labeling, directions for preliminary (patch) testing, and restrictions against use in or near the eye. The EDA diligently enforces the rules governing color additives and limits the use of, or even dehsts colorants deemed unsafe. The Hst of substances specifically prohibited for use in cosmetics is short. 

Melamine ia a skin test on rabbits produced neither local irritation nor systemic toxicity. As a 10% solution ia methylceUulose, it caused no irritation ia the eyes of rabbits. Human subjects were given patch tests with melamine. No evidence of either primary irritation or sensitization was found. Such results suggest that melamine crystal may be handled ia ordinary iadustrial use without special hygienic precautions. 

Skin irritation potential is assessed by patch tests. More serious than simple irritation is the potential of a product to cause sensiti2ation, ie, to cause a subject to become allergic to even very small amounts of the product. 

Photosensiti2ation, the potential of a product to cause sensiti2ation in the presence of sunlight, is similarly evaluated by taking a patch test on guinea pigs before and after exposure to uv radiation (141). 

Neoprene Type TW was shown to have low oral toxicity in rats. The LD q was found to be in excess of 20,000 mg/kg. Human patch tests with Types GN, W, WRT, and WHV showed no skin reactions (169). The FDA status of Du Pont Neoprene polymers is described (172). Although polychloroprene itself has not been shown to have potential health problems, it should be understood that many mbber chemicals that may be used with CR can be dangerous if not handled properly. This is particularly tme of ethylenethiourea curatives and, perhaps, secondary amine precursors often contained in sulfur modified polychloroprene types. Material safety data sheets should be consulted for specific information on products to be handled. 

Skin tolerance was tested on rabbits. A 1 % alkanesulfonate solution applied five times did not produce any irritation on the rabbits skin. The same results were obtained by the closed patch test carried out with human test subjects in a hospital. The good dermatological properties were also confirmed by the Polano test (arm immersion test). 

Among the large amount of data based on different animals some studies are worth mentioning. Brown and Muir [367] studied alcohol sulfates based on coconut alcohol and on Dobanol 23, neutralized with sodium, ammonium, monoethanolamine, and triethanolamine. The study was carried out by occlusive patch tests on albino rabbits and open patch tests on albino rabbits and albino guinea pigs. Solutions at 0.1 % concentration did not cause any reaction... 

Van Paassen [57,67] reported a synergistic decrease of the skin and eye irritation level of sodium lauryl ether sulfate by combination with lauryl ether carboxylates. The investigations have been carried out using the Draize eye irritation test and human patch test (Tables 13 and 14). Furthermore, measurements by in vitro methods, the Zein test, and the red blood cell test show low to no irritancy [251-253]. 

FIG. 7 Skin irritation according to the human patch test of alkyl ether carboxylic acids compared to other mild cosurfactants. CFTA-names 1, cocamidopropylbetaine 2, sodium PEG-6 cocamide carboxylate 3, sodium laureth-11 carboxylate 4, cocoamphocarboxypropionate 5, protein hydrolyzate 6, disodium laureth-3 sulfo-succinate SLES, sodium laureth sulfate. (From Ref. 68.)... 

Dermal Effects. Based on a skin patch test, allergic (contact) dermatitis to methyl parathion occurred in a farmer (Lisi et al. 1987). 

The only study located regarding immunological effects in humans after dermal exposure to endosulfan was an account of the results of patch tests on the backs of 14 farm workers with work-related dermatitis and 8 controls who were not exposed to pesticides (Schuman and Dobson 1985). Skin sensitization was not observed in any of the subjects following a 48-hour, closed-patch exposure to an unspecified amount of 0.1 % endosulfan in petrolatum. 

Numerous positive delayed skin tests in patients with contrast medium-induced non-immediate skin reactions have been reported when the patients were tested with the culprit contrast medium [summarized in 1]. In a large European multicenter study, 37% of patients with non-immediate reactions were positive in delayed IDEs and/or patch tests [13]. The majority of the patients also reacted to the culprit contrast medium and also to other, structurally similar RCM. Notably, in more than 30% of those skin test-positive patients a RCM had been administered for the first time. Thus, there is a lack of a sensitization phase. Again it may be hypothesized that these previously non-exposed patients may have already been sensitized. Different patterns of RCM cross-reactivity indicate that several chemical entities could be involved. No positive skin tests have been obtained with other contrast medium excipients, such as ethylenediaminetetraacetic acid (EDTA), and only rarely patients have been found to react to inorganic iodide. 

The further allergologic workup is recommended should be performed within 6 months after the reaction [13]. Both delayed IDTs and patch tests are frequently positive, when read after 48 and 72 h (in case of local pruritus or erythematous plaques optionally at other time points, e.g. 24 h, 96 h). Since some patients tested positive with only one of these tests, it is recommended to use both tests in parallel to enhance test sensitivity (table 3). Patch tests should be conducted with undiluted RCM, whereas 10-fold diluted products in physiologic saline had been recommended when performing delayed IDTs. IDTs and late readings with undiluted RCM may be discussed in non-severe reactions to increase sensitivity, however this has not been evaluated in a sufficient number of controls. A panel of several different RCM should be tested to identify skin test-negative substances. 

True IgE-mediated anaphylactic reactions to LAs are extremely rare [11-13]. Only single cases have been reported in the literature with positive prick tests [ 14,15]. A case of a positive open patch test in a patient suffering from contact urticaria after topical application of lidocaine, pilocaine mixture (Emla cream) might represent a true IgE-mediated allergy [16]. The maj ority of immediate-type reactions are non-immune in nature. 

In a study performed by Ruzicka et al. [23], 104 patients with positive patch tests to LAs and a history of contact dermatitis were tested with LA in a prick test and in an intradermal setting. All prick tests remained negative. There were 9 persons positive for procaine in the intradermal test and 3 positive for butanilicaine. There was no correlation to history in the patients with skin tests and no correlation between patch test results and results of the intradermal test [23]. 

Breit S, Rueff F, PrzybiUa B Deep impact contact allergy after subcutaneous injection of local anesthetics. Contact Dermatitis 2001 45 296-297. Orasch CE, Helbling A, Zanni MP, Yawalkar N. Hari Y Pichler WJ T-cell reaction to local anaesthetics relationship to angioedema and urticaria after subcutaneous application-patch testing and LTT in patients with adverse reaction to local anaesthetics. Clin Exp Allergy 1999 29 1549-1554. 

Ruzicka T, Gerstmeier M, PrzybiUa B, Ring J Allergy to local anesthetics comparison patch test with prick and intradermal test results. J Am Acad Dermatol 1987 16 1202-1208. 

As discussed imder dermal effects, people can develop hypersensitivity to trichloroethylene. The effects observed in hypersensitive individuals include skin effects (Conde-Salazar et al. 1983 Nakayama et al. 1988 Phoon et al. 1984 Waller et al. 1994) and liver effects (Phoon et al. 1984). Dermal sensitivity was confirmed with patch testing in only two cases (Conde-Salazar et al. 1983 Nakayama et al. 1988). The woman described by Conde-Salazaer et al. (1983) reacted positively to both vapor exposure and a dermal application of 5% trichloroethylene in olive oil. 

Discuss testing that may need to be performed to suggest or confirm the etiologic agent (patch testing). 

Only a few in vivo dermal toxicity studies have been reported so far. Huczko and Lange [50] evaluated the potential of raw CNTs to induce skin irritation by conducting two routine dermatological tests (patch test on 40 volunteers with allergy susceptibilities and Draize rabbit eye test on four albino rabbits). Koyama etal. [51] showed the biological responses to four different types of carbon nanotubes (SWNTs, two types of MWNTs with different diameters, and cup-stacked carbon nanotubes) after their subcutaneous implantation in mice. Both tests [50, 51] showed no or poor irritation effects. However, the in vitro studies in epidermal cell lines exposed to CNTs, and also a more recent report on the toxic outcomes of topical exposure of mice to SWNTs [46], have raised concerns over these assessments. Clearly, this is an area requiring further scientific evaluation. 

CNTs Arc discharge Human Patch test 96 h None [50]... 

Morris SD, Rycroft RJ, White IR, Wakelin SH, McFadden JP Comparative frequency of patch test reactions to topical antibiotics. Br J Dermatol 2002 146 1047-1051. 

Marks JG Jr, Belsito DV, DeLeo VA, Fowler JF Jr, Fransway AF, Maibach HI, Mathias CG, Pratt MD, Rietschel RL, Sherertz EF, Storrs FJ, Taylor JS North American Contact Dermatitis Group patch test results for the detection of delayed-type hypersensitivity to topical allergens. J Am Acad Dermatol 1998 38 911— 918. 

Chromium is the most common skin sensitizer known to human males (Haines and Nieboer 1988). Up to 26% of all males tested and 10% of females were sensitive to potassium dichromate patch tests. The highest frequency of chromium-sensitive individuals was found in Brazil, Belgium, and North America, especially Detroit and New Orleans. Frequency of chromium dermatitis was... 

Kimber, I., Hilton, J. and Botam, P. A., Identification of contact allergens using the murine local lymph node assay comparison with the Buehler occluded patch test in guinea pigs, J. ofAppl. Toxicol., 10, 173, 1990. 

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