Sylvie Cupferman

Experimental elicitation of contact allergy from a diazolidinyl urea‐preserved cream in relation to anatomical region, exposure time and concentration

The elicitation potential of the cosmetic preservative diazolidinyl urea was studied in formaldehyde‐ and diazolidinyl urea‐sensitized volunteer patients using a stepwise controlled exposure design. The test product was a facial moisturizer, preserved with varying concentrations of diazolidinyl urea, ranging from 0.05% to 0.6%. A repeated open application‐like exposure test was performed on volunteers and a control group with the test product containing increasing preservative concentrations, on arm, neck and face, sequentially, for 2 weeks or until dermatitis developed. The preservative action in the cream at different test concentrations was tested in microbial challenge tests and was found effective at all concentrations tested. The study established a non‐eliciting concentration of diazolidinyl urea of 0.05% in formaldehyde‐sensitive patients and showed that the skin reactivity depends on the anatomical region, increasing from the upper arm to neck and, possibly, to the face. The study design, beginning on the upper arm and moving on to the neck and face seems to be relevant for the study of reactions to cosmetic products. A clear dose–response relationship was seen regarding preservative concentration in the product.

ROAT : morphology of ROAT on arm, neck and face in formaldehyde and diazolidinyl urea sensitive individuals

The morphology of early allergic contact dermatitis reactions was studied in formaldehyde allergic individuals exposed to a cream product preserved with 4 different concentrations of diazolidinyl urea. The study was made using a dose‐escalating design in 3 different anatomical regions, the upper arm, neck and face. On the arm and neck, the dominant initial morphology was an eczematous papular eruption. In the face, the initial skin changes were more homogeneous and infiltrated erythema.

Method for evaluation of the efficacy of antimicrobial preservatives in cosmetic wet wipes.

Many cosmetic formulations are now available in the form of wet wipes packaged in sealed sachets or packets. Like the majority of cosmetic products having an aqueous phase, wipes are susceptible to microbial contamination and require the addition of preservatives. The efficacy of such preservatives can be evaluated using a standard challenge test performed on the wetting liquid but this test cannot be regarded as representative for this new type of formulation. The method presented here evaluates the efficacy of preservatives used in wet wipes kept in their original packaging. Dried inoculums were prepared by membrane filtration followed by drying in an incubator. The method is applicable to bacteria (Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis), Bacillus cereus spores and fungi (Candida albicans and Aspergillus niger). These inoculated carriers were inserted between two wipes in the original package, which was then re‐sealed immediately. The test requires one dry inoculum per packet and one packet for each control or test. After incubation at 22.5°C for 1, 2, 7, 14 or 28 days and, for the control, immediately after insertion of the membrane (time 0), microorganism counts were performed on the germ‐carrier membranes as well as on adjacent wipes, after transfer into a suitable neutralizing agent. The membranes were shaken in the presence of glass beads and microorganisms were dissociated from the wipes by means of a Stomacher. The supernatants recovered after being left to stand for 20 min are counted by pour plate method or membrane filtration. The feasibility of the method was demonstrated for each of the seven above‐mentioned strains. The repeatability and reproducibility of the results obtained is similar to that obtained for preservative efficacy tests in the Pharmacopoeias. The lethal rate of microorganisms during the preparation of dry inoculums ranges from 50 to 90% depending on the strain and the test (generally, a spontaneous reduction of about 1 log up to a maximum of 2 log). The recovery rate for microorganisms from dry inoculums (on membranes) at time 0 (control = T0) is around 90%, regardless of the strain or the test. The number of microorganisms recovered from the wipes (W0) is between 2 and 10% of the number recovered from membranes (T0) and may be considered negligible. Application of this method to different types of wipes demonstrates that the efficacy of preservatives, expressed as the logarithmic reduction in the number of microorganisms at each time point, depends on the type of wipe and on the strain tested. The results obtained are considerably different from those found with the standard challenge tests applied to wetting liquids for wipes. The differences found confirm the need for a specific method applicable to wipes.

Growth, survival and inactivation of Pseudomonas aeruginosa and Staphylococcus aureus strains of various origin in the presence of ethanol

The influence of ethanol on the behaviour of Pseudomonas aeruginosa and Staphylococcus aureus strains was evaluated throughout this study. Strains of different origin were used: collection, clinical and industrial strains were selected. Concentrations of ethanol from 0 to 20% (v/v) were evaluated by automated optical density measurements and by enumeration. When growth conditions were observed, predictive microbiology models were used to assess quantitatively for the ethanol effect. Primary modelling of kinetics was performed to determine growth rate values; secondary modelling was performed on these growth rates as influenced by ethanol, and minimum inhibitory concentrations of ethanol were determined for each strain. Staphylococcus aureus strains were more resistant to ethanol than P. aeruginosa strains, in growth conditions as well as in inactivation conditions. Furthermore, clinical S. aureus strains were more resistant than the collection strain. The method was promising for management of microbiological safety in cosmetics.

Antimicrobial activity of Butyl acetate, Ethyl acetate and Isopropyl alcohol on undesirable microorganisms in cosmetic products.

The microbiological contamination risk of a cosmetic product has to be assessed by the manufacturer, according to the composition, to determine whether microbiological testing is required. Certain ingredients in cosmetic formulations help to create an environment hostile towards microbial growth. In this study, the influence on microbial survival of some solvents used in nail varnishes was evaluated. The purpose of this study was two‐fold. The first was to define the thresholds to be considered for the exemption of products from microbiological testing. The second was to assess the cross‐contamination risk linked to the use on successive consumers of solvent‐based products in beauty salons.

Bactericidal activity of ammonia and monoethanolamine on Pseudomonas aeruginosa and Staphylococcus aureus strains of various origins

Microbiological risk of cosmetic products has to be assessed by the manufacturers to determine whether microbiological testing is required, according to the composition of a given product. The use of certain ingredients in cosmetic formulations will help to create a hostile environment towards microbial growth. In this study, the influence of some cosmetic ingredients on bacterial survival was evaluated.