Contact sensitizing potential of pyrogallol and 5-amino-o-cresol in female BALB/c mice

Abstract

Hair dye components such as pyrogallol and cresol have been shown previously to promote allergic reactions such as rashes, dermal inflammation, irritation and dermatitis. The objective of this study was to determine the contact sensitization potential of pyrogallol (PYR) and 5-amino-o-cresol (AOC) when applied dermally to female BALB/c mice. Measurement of the contact hypersensitivity response was initially accomplished using the local lymph node assay. For PYR, significant increases in the proliferation of lymph node cells were observed at concentrations of 0.5% (w/v) and higher. For AOC, borderline increases, albeit significant, in auricular lymph node cell proliferation were observed at 5% and 10%. Results from the irritancy assay suggested that PYR, but not AOC, was an irritant. To further delineate whether PYR was primarily an irritant or a contact sensitizer, the mouse ear swelling test (MEST) was conducted. A significant increase in mouse ear thickness was observed at 72 h following challenge with 0.5% PYR in mice that had been sensitized with 5% PYR. In contrast, no effects were observed in the MEST in mice sensitized and challenged with the highest achievable concentration of AOC (10%). Additional studies examining lymph node subpopulations and CD86 (B7.2) expression by B cells further support the indication that PYR was a sensitizer in BALB/c mice. The results demonstrate that PYR is both a sensitizer and an irritant in female BALB/c mice. However, the contact sensitization potential of AOC is minimal in this strain of mouse.

Introduction

It is estimated that one in three women above the age of 18 and one in ten men above the age of 40 use some type of hair coloring. Permanent coloring accounts for approximately 70% of the dollar volume of the retail market and 85% of the professional market (Corbett, 1988) for hair care products. The use of synthetic colors in hair dyes has been brought to the attention of the public because some ingredients can induce rash, dermal inflammation, irritation, and dermatitis, or even promote cancer (Shvedova et al., 2000, Ferrari et al., 2005, Khumalo et al., 2006, O’Connell et al., 2010).

Pyrogallol (PYR), or pyrogallic acid (1,2,3-trihydroxybenzene), colorless crystals or laminae when freshly prepared, rapidly assume a darker color upon oxidation. Both PYR and its oxidative product, purpurogallin, are mutagenic (Ben-Gurion, 1979, Takemura et al., 2010). Although the European Community has PYR on the list of banned substances as ingredients for cosmetics, it is still being used in many other countries (Takemura et al., 2010, ANVISA, 2013), and positive responses to PYR continue to be reported in patients who were suspected to have allergic contact dermatitis following exposure to hairdressing chemicals (Basketter and English, 2009, Wang et al., 2011). In addition, PYR has found extensive use in industrial and commercial processes, including uses in photograph developing, in the manufacture of dyes, in fruit storage, as a component of hair and fur dye, as a tanning agent for leather, and in the production of a novel class of carbamate insecticides (Windholtz, 1976, Dresslerr and Holter, 1982, Mercado-Feliciano et al., 2013, Jing et al., 2013). PYR concentrations in hair dyes and colors typically range from 0.25 to 0.38% by weight (Clayton and Clayton, 1981), and the maximum concentration allowed is 5% (ANVISA, 2013). Moreover, PYR was used as a topical therapy for chronic plaque psoriasis, and it is still used in some places to treat treatment resistant psoriasis (Gruner et al., 1992, Upadhyay et al., 2010).

5-Amino-o-cresol (AOC) is an oxidative intermediate used in hydrogen peroxide-induced coupling reactions in permanent hair dye formulations (Akerson et al., 1994). According to the Food and Drug Administration (FDA) product formulation data, AOC was used in 149 out of 960 hair dye formulations in 1986, and it is still being used worldwide (Chemland, 2013). AOC concentrations in hair dyes range between 0 and 5%. According to a study by Beck et al. (1994), both pig skin (in vitro) and rat skin (in vivo) are permeable to AOC. In the report from the Scientific Committee on Consumer Products; Opinion on: 4-Amino-2-hydroxytoluene (Opinions SCCP, 2006), two murine studies regarding the skin sensitization potential of AOC have been cited; however, only one mouse strain (CBA/Ca01aHsd) was used. Thus, further evaluation of AOC sensitizing potential in a different mouse strain was useful, especially when only 4 of the 10 female albino Hartley guinea pigs showed evidence of a skin sensitization in another study cited in the same report.

The objective of the present study was to evaluate the contact sensitization potential of both PYR and AOC when applied dermally to female BALB/c mice using the well-established local lymph node assay (LLNA), the irritancy assay (IRR), and the mouse ear swelling test (MEST). In addition to the LLNA and MEST, additional information on the sensitization potential of a compound can be obtained from flow cytometric analysis of the draining lymph nodes (Sikorski et al., 1996, Manetz and Meade, 1999, Gerberick et al., 2002, Auttachoat et al., 2011). Thus, a detailed evaluation of lymph node subpopulations and CD86 (B7.2) expression was also conducted for PYR. The results demonstrate that PYR is both a sensitizer and an irritant in female BALB/c mice. In contrast, data from the LLNA, IRR and MEST suggest that the contact sensitization potential of AOC is minimal.