Calcium dibenzoate

Endpoint summary

Description of key information

No skin sensitisation study with Calcium dibenzoate is available, thus the skin sensitisation potential will be addressed with existing data on the individual moieties calcium and benzoate.

Calcium dibenzoate is not expected to have a skin sensitising activity, since the two moieties calcium and benzoic acid have not shown any skin sensitisation potential in experimental testing.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Calcium dibenzoate

Calcium dibenzoate is not expected to have a skin sensitising activity, since the two moieties calcium and benzoic acid have not shown any skin sensitisation potential in experimental testing. Further testing is not required.

Thus, Calcium dibenzoate is not to be classified according to regulation (EC) 1272/2008 and its subsequent amendments as skin sensitising.

 

Calcium

Evaluation of the sensitization potential of a substance was usually carried out in animal models. Nowadays, there is much interest in reducing and ultimately replacing current animal tests. The human cell line activation test (h-CLAT) and the ARE-Nrf2 luciferase test method were recently adopted as alternative methods for skin sensitization. Both test systems are based on human cell lines, such as the human monocytic leukaemia cells THP-1 and the KeratinoSens™ cells which are cultured either in RMPI-1640 medium or DMEM (OECD guideline No. 422D and 422E). Both media are supplemented with calcium salts at concentrations ranging from 2.5 to 5.0 mM. These methods were validated and accepted under these conditions and demonstrate that in vitro cell culture systems are dependent on calcium containing media.

Also due to its essential functions in skin cells and experience from its widespread use in skin cosmetics, a sensitising potential of calcium can be excluded: Calcium is known for its key role in many regulatory functions in the skin. Calcium is mostly found in the outermost layer, the epidermis, where it is involved in barrier function repair and skin homeostasis (Dendaet al.,2003). Within the epidermis, keratinocytes have a different need for calcium concentrations. Keratinocyte differentiation throughout the epidermis is in part mediated by a calcium gradient, increasing from the stratum basale until the outer stratum granulosum, where it reaches its maximum. “Calcium concentration in the stratum corneum (SC) is very low because the relatively dry SC, with its extracellular lipid content, is not able to dissolve the ions. After disruption of the permeability barrier, an influx of water into the SC occurs and the calcium ion gradient is lost. This depletion of calcium regulates lamellar body exocytosis (Lee et al., 1992; Menon et al., 1985; Menon et al., 1991). Disturbed regulation of calcium metabolism and increased transepidermal water loss (Lavrijsen et al., 1993) is observed in Darier’s and Hailey– Hailey diseases, which are both characterized by loss of adhesion between suprabasal epidermal cells” (Prokschet al.,2008). Beside the fact, that calcium is a very important regulator of protein synthesis in the epidermis, including regulation of transglutaminase 1 activity (Hitomi, 2005) and cell–cell adhesion, the calcium gradient described above is involved in keratinocyte differentiation and as such considered as a key regulator in the formation of the epidermal layers (Proksch et al., 2008).

The turnover rate of the keratinocytes slows down with increasing age which is associated with thinning of the epidermis, elastosis and a decreased barrier function. Since the differentiation of the keratinocytes is calcium dependent, calcium plays a crucial role in the aging epidermis. Therefore, many calcium containing cosmetic products, especially anti-ageing products, are on the market. For example one of the long-lasting synthetic semi-permanent dermal fillers is calcium hydroxylapatite suspended in an aqueous carboxymethylcelluose gel carrier or calcium pantothenicum cream for regeneration of damaged skin. Radiesse® is one of these subdermal fillers, whose principal component is synthetic calcium hydroxylapatite (CaHA). Depending on injection site up to 4 mL of this product is injected (Jacovella, 2008). “The semi-solid nature of the product is created by suspending CaHA microspheres of 25-45 micron diameter in a gel carrier that consists primarily of sterile water and glycerin. The gel structure is formed by the addition of a small amount of carboxymethylcellulose (USP). The gel is dissipated in vivo and replaced with soft tissue growth, while the CaHA remains at the site of injection (Bioform Medical Inc. 2007)” (Jacovella, 2008). According to Flaharty (2000) the biocompatibility of CaHA has been tested in preclinical studies, and it has been shown to be non-toxic and non-mutagenic (Flaharty 2000).

Calcium hydroxide, calcium phosphate as well as calcium stearate are known ingredients of many commercially available products. “Calcium stearate was reported to be in 23 preparations in 1976, with the largest single use occurring in eyebrow pencils; concentrations ranged from >25 % to 50 %. In 2001, calcium stearate was reportedly used in 107 cosmetic preparations (FDA, 2001), with the largest single use occurring in eye shadow at concentrations that range from 0.2 % to 10 % (CTFA, 2001)” (The Cosmetic Ingredient Review (CIR) Expert Panel, 2001). The CIR Expert Panel evaluated the scientific data and concluded that calcium stearate and other stearates were safe for use in cosmetics and personal care products. In 2001, as part of the scheduled re-evaluation of ingredients, the CIR Expert Panel considered available new data on the stearate compounds and reaffirmed the above conclusion. According to the Regulation No. 1223/2009 of the European Parliament and of the Council on Cosmetic Products the use of calcium stearate is allowed in colorants and preservatives (EC No. 1223/2009 Annex IV and V).

 

Overall, calcium is essential for epidermal differentiation and used in high concentrations in cell culture media for validated in vitro skin sensitization experiments. In addition, according to the Regulation (EC) No. 1223/2009 the use of calcium in colorants and preservatives in cosmetic products is approved and allowed. Based on the top-dermal and also intradermal use of calcium substances, skin sensitising properties or intolerance to the abundantly available essential element can safely be excluded. Therefore, further testing should not be considered, inter alia for reasons of animal welfare. In conclusion, conduct of a skin sensitization study on calcium is considered to be scientifically unjustified (in accordance with regulation (EC) 1907/2006, Annex XI, Section 1.1.2, 1.1.3 and 1.2).

 

Benzoic acid

 Several sensitisation studies including LLNA, GPMT and Buehler tests revealed no sensitising potential of benzoic acid.

1) Negative in a LLNA study (Geberick, 1991) with Mice. Key study (as LLNA considered most sensitive study type).

2) A dermal sensitization study using the Buehler test was conducted under GLP according to EPA guideline using guinea pig (Bier, 1979). Supporting study. Benzoic acid is neither an irritant nor sensitizer when applied to guinea pigs.

3) Negative in a mouse ear swelling test (Gad, 1985).

4) Negative in a GPMT test (Gad, 1985).

5) Negative in a Buehler test (Gad, 1985).

 

Two studies in guinea pigs (Lahti 1984, 1985) investigating the potential of benzoic acid to induce contact urticaria were positive. However no effects were reported in rats and mice. The test design is similar to the induction phase of the mouse ear swelling test.

 

In addition to animal data, many human studies are available investigating effects of benzoic acid on skin, including immunological and non-immunological responses. Most studies are of limited quality and benzoic acid is used as a standard substance to elicit a skin reaction in humans.

Benzoic acid does induce skin effects in healthy adults and children after topical application.

An in vitro test (Wilhelm 2001) on cytotoxicity (NR uptake) with human keratinocytes showed an IC50 of 20 mmol. In the same study benzoic acid did not show any irritant properties to human skin (dose 20 mmol).

No definite conclusion on the mechanism responsible for induction of skin reactions can be drawn. Both in persons with history of atopic eczema as well as in healthy (non-atopic) subjects, skin reactions were increased after application of benzoic acid (Lahti 1978).

Therefore, benzoic acid is not considered to be a skin sensitiser.

 

References

Bioform Medical Inc. Regulatory issues. 2007. Accessed October 25, 2007. URL: http: //www.radiesse.com.

Cosmetic, Toiletry, and Fragrance Association (CTFA), 2001. Product use concentration information for Stearate Salts; memorandum dated December 174.

Denda M, Fuziwara S and Inoue K. Influx of Calcium and Chloride Ions into Epidermal Keratinocytes Regulates Exocytosis of Epidermal Lamellar Bodies and Skin Permeability Barrier Homeostasis. Journal of Investigative Dermatology. 2003; 121: 362–367

EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2015. Scientific Opinion on Dietary Reference Values for calcium. EFSA Journal 2015;13(5):4101, 82 pp. doi:10.2903/j.efsa.2015.4101

Flaharty P. Radiance. Facial Plast Surg. 2000;20:165–9

Food and Drug Administration (FDA), 2001. Frequency of use of cosmetic ingredients. FDA Database, Washington, DC: FDA.

Hitomi K. Transglutaminases in skin epidermis. Eur J Dermatol 2005: 15: 313–319.

Jacovella, P.F., Use of calcium hydroxylapatite (Radiesse®) for facial augmentation, Clin Interv Aging. 2008 Mar; 3(1): 161–174.

Lavrijsen A P, Oestmann E, Hermans J, Bodde H E, Vermeer B J, Ponec M. Barrier function parameters in various keratinization disorders: transepidermal water loss and vascular response to hexyl nicotinate. Br J Dermatol 1993: 129: 547–553.

Lee S H, Elias P M, Proksch E, Menon G K, Mao-Quiang M, Feingold K R. Calcium and potassium are important regulators of barrier homeostasis in murine epidermis. J Clin Invest 1992: 89: 530–538.

Menon G K, Grayson S, Elias P M. Ionic calcium reservoirs in mammalian epidermis: ultrastructural localization by ion-capture cytochemistry. J Invest Dermatol 1985: 84: 508–512.

Menon G K, Elias P M. Ultrastructural localization of calcium in psoriatic and normal human epidermis. Arch Dermatol 1991: 127: 57–63.

Proksch, E.; Brandner, J. M.; Jensen, J.M., The skin: an indispensable barrier. Experimental Dermatology 2008; 17: 1063–1072.

The Cosmetic Ingredient Review (CIR) Expert Panel, Annual Review of Cosmetic Ingredient Safety Assessment- 2001/2002; International Journal of Toxicology, 22 (Suppl. 1): 1-35, 2003

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

As the two moieties of Calcium dibenzoate, i.e. calcium and benzoic acid, are not sensitising, Calcium dibenzoate in all probability has also no sensitising activity.

Thus, Calcium dibenzoate is not to be classified according to regulation (EC) 1272/2008 and its subsequent amendments as skin sensitising.