IPBC – a globally-approved fungicide

This approval expands the global acceptability of IPBC for cosmetic products, as shown in Table 7. One of the fastest growing areas of personal care product offerings is wipes. Today, wipes are available with treatments that include insect repellent, cleansing, treatment (self-tanning, acne) and disinfecting. These products are particularly challenging to preserve, especially against fungal growth.

The ability to effectively preserve these non-woven substrate products is often difficult. Some of the challenges include preservatives irreversibly binding to the substrate and the product having susceptibility to fungi such as cellulose degrading moulds.

Additionally, towelette products that are sold in bulk, such as facial wipes, may be packaged in a manner that allows for considerable product insult over time. In the Asian marketplace, facial masks are also experiencing significant demand and require an effective, yet non-irritating preservative. The fungicidal activity of IPBC provides a much needed solution for ever popular market segments in need of efficient and highly effective preservation.

The expanded use profile of IPBC is supported by its long history of safe use that is based on a comprehensive toxicology database and significant use experience. IPBC has been tested extensively to meet personal care regulatory standards in various key regions around the world. This article will expand on the safety profile, regulatory acceptance, use and fungicidal performance of IPBC in personal care products.

IPBC versus parabens

Historically, parabens have been the most widely used fungicides in personal care products. In 2003, methylparaben, propylparaben and butylparaben were the mostly widely used preservatives in cosmetics as reported to the FDA, with their usage in the US accounted for in more than 15,000 formulations (57.7% of the total number reported).2 In that same analysis, IPBC was reportedly used in 227 US formulations. While parabens continue to be a more popular choice, studies have shown that IPBC has significantly lower MIC values than those of parabens, as shown in Table 1.

Preservative efficacy testing methodology

Preservative challenge studies were conducted using a particular liquid cosmetic preservative product that is a combination of DMDM Hydantoin (DMDMH) and IPBC. DMDMH is a widely used broad spectrum bactericide with little to no fungicidal activity,4 while IPBC is a highly effective fungicide with very weak bactericidal properties.5 The testing was performed utilising commercial personal care formulations for two leave-on products, a rinse-off product and in a formulated personal care wipe. For the three aqueous products, Lonza’s standard challenge test method6 was employed, with the addition of a re-inoculation at Day 7. A fungal pool consisting of equal amounts of Candida albicans, ATCC 10231 and Aspergillus niger, ATCC 16404 was used. To each 40 gram sample of test product, the fungal pool was added to yield approximately 5.0 x 105 colony forming units (CFU) per gram of product. The samples were mixed well and sampling was done at Day 0 and Day 7. After sampling on Day 7, the samples were inoculated again in the same manner with a freshly prepared fungal inoculum. Samples were taken at Day 7 (after the rechallenge) and at Days 14 and 28 post the initial inoculation.

A preservative efficacy test was also conducted on a formulated personal care wipe, with the preservative system added to the aqueous add-on portion of the product and the aqueous portion subsequently applied to the non-woven substrate according to the manufacturer’s instructions. The test was conducted following CTFA Method M-5, “Methods for Preservation Testing of Non-woven Substrate Personal Care Products”. A fungal inoculum pool was used in the aqueous product studies with a re-challenge step at Day 14. Additional sampling points were also taken, as shown in Table 5.

Leave-on products

A commercial moisturiser (oil/water emulsion) and a commercial, non-ionic surfactant based facial serum with botanicals were utilised in preservative challenge testing to determine the efficacy of IPBC in representative leaveon products. The results of this testing, provided in Tables 2 and 3, demonstrate the effectiveness of the preservative system in controlling the microorganisms, with counts of less than 10 colony forming units (CFU) of fungi per gram of test product at Day 7 post each inoculation.

Rinse-off products

The preservative efficacy of IPBC was determined in a commercial, anionic surfactant based facial cleanser, representing a personal care rinse-off product. The results shown in Table 4 illustrate the applicability of the preservative system for this product category with a recovery of less than 10 CFU of fungi per gram of test product at Day 7 post each inoculation.

Formulated personal care wipes

The data provided in Table 5 demonstrates that even at levels at or below 100 ppm IPBC, the preservative is suitable for a product such as personal care wipes that require robust and effective preservation against fungi. The product utilised in this testing is a commercially available personal care wipe comprising an air-laid non-woven substrate.

Formulation guidelines

IPBC is a halogenated unsaturated organic compound (Fig. 1). Pure IPBC may impart an undesirable colour to personal care preparations. However, such changes are unlikely at the typical low usage levels. IPBC is commercially available in powder, glycol based and aqueous based mixtures.

The solubility of IPBC is poor in water and thus the glycol based mixtures or powder concentrate products should be added to glycols prior to incorporation into the finished product. The aqueous based IPBC products utilise a proprietary encapsulation process that improves water solubility so that it may be added directly to aqueous systems. This is particularly useful for manufacturing processes where in-line mixing is employed.

IPBC is compatible with virtually all surfactant systems. It will be deactivated by strong oxidising or reducing agents, and by extremes in pH. It is stable in personal care preparations with a pH between 3 and 9, and it is important to ensure that IPBC is in the aqueous phase of the final product. During processing, preservatives containing IPBC are best incorporated during the cool down phase, at temperatures not exceeding 50°C. Typical effective use levels for active IPBC is 50 – 200 ppm in personal care formulations, including base solutions for wipe products. IPBC is also available in blended products with known bactericides, such as DMDMH, resulting in an effective broad spectrum preservative with low use cost.

Regulatory summary

Table 6 provides a summary of the global regulations, based on currently available information, for IPBC as a functional preservative in cosmetics, including use levels and restrictions.

Toxicology summary

IPBC has a comprehensive toxicology information package that includes the Cosmetic Ingredient Review (CIR) Final Report, US Environmental Protection Agency (EPA) Re-registration Eligibility Decision (R.E.D.) review, EU Scientific Committee on Consumer Products (SCCP) Review, and Japanese MHLW Review.

The CIR Expert Panel concluded that IPBC is approved for use as a cosmetic ingredient at concentrations of 0.1% or less for leave-on and rinse-off products, including lip and oral care products.8 IPBC should not be used in products that are to be aerosolised.

The US EPA has stated that IPBC should not be a threat for surface and ground water because it rapidly degrades in soil and aquatic environments.9 Studies conducted to determine the toxicology of IPBC in personal care products include acute toxicology, subchronic toxicology, chronic toxicity/carcinogenicity, developmental toxicology, reproductive toxicology, mutagenicity, metabolism, and skin penetration studies. Results from these studies indicate that IPBC is non-carcinogenic and non-mutagenic. No reproductive or developmental effects were reported.10

Clinical assessment of IPBC included tests for skin irritation (primary and cumulative), Human Repeat Insult Patch Test (HRIPT), photosensitisation, human cross sensitisation, comedogenicity, photocontact allergenicity, and phototoxicity. The results from these tests are in Table 7.

Overall summary

IPBC products are easy to incorporate into all surfactant systems and a water-based IPBC product is particularly useful during in-line mixing operations. Unlike some alternative products, IPBC is compatible with most personal care raw materials and no discoloration or pH drift is observed at use levels. The low MIC values for IPBC compared to parabens offer formulators an opportunity to lower the level of fungicidal preservatives from traditional levels. For the rapidly growing wipes market, IPBC provides an economical and highly effective fungicide for a product category particularly susceptible to fungal contamination. Solvent-based IPBC and water-based IPBC products currently represent the most appealing alternative to the use of parabens for personal care products, based on IPBC’s demonstrated preservative efficacy, safety, compatibility, and regulatory acceptance.

References

1 Branna T. A preservative update, Happi 41 (5) 89-92 (2004).

2 Steinberg D. Common Preservatives, Chapter 1 in Preservatives for Cosmetics, Carol Stream, IL: Allured Publishing (2006).

3 Gruening R. IPBC Preservative Combination Systems for Material Protection, Cosmetics and Toiletries 112, 59-68 (1997).

4 Appendix 2: Commonly Used Preservatives in Cosmetic Microbiology in Cosmetic Microbiology, A Practical Handbook, D Brannan, ed, Boca Raton, FL: CRC Press (1997) pp 254-255.

5 Steinberg D. Common Preservatives, Chapter 2 in Preservatives for Cosmetics, Carol Stream, IL: Allured Publishing (2006).

6 Lonza SOP 408-01-3 (1998).

7 CTFA International Regulatory Database. Available Only to CTFA Members. Accessed November 17, 2006.

8 International Journal of Toxicity, Volume 17 (Suppl. 5), 1998, pages 1-37.

9 US EPA_United States Environmental Protection Agency. R.E.D. Reregistration Eligibility Decision. Facts: 3-Iodo-2-Propynyl Butylcarbamate (IPBC).; 1997; EPA-738-F-7-003.

10 International Journal of Toxicity, Volume 17 (Suppl. 5), 1998, pages 1-37.

11 Ibid.

ABSTRACT
The recent approval of 3-Iodo-2-propynyl butyl carbamate (IPBC) in Japan has expanded the global acceptability of IPBC as a fungicide for personal care products.