Methylisothiazolinone in rinse-off products causes allergic contact dermatitis: a repeated open-application study.

BACKGROUND: In recent years, the prevalence of contact allergy to the preservative methylisothiazolinone (MI) has increased dramatically. Cosmetic products are one of the major sources of exposure. OBJECTIVES: To examine whether allowed concentrations of MI in cosmetic rinse-off products have the potential to cause allergic contact dermatitis. METHODS: Nineteen MI-allergic subjects and 19 controls without MI allergy applied two liquid hand soaps five times per day on areas of 5 × 10 cm(2) on the ventral side of their forearms. One soap contained 100 ppm MI, the maximum allowed concentration in cosmetics, and was used by 10 allergic subjects and all controls. Another liquid soap with 50 ppm MI was used by nine allergic subjects. As the negative control, all subjects used a similar soap that did not contain MI. The repeated open applications proceeded until a positive reaction occurred or up to 21 days. The study was conducted in a randomized and blinded fashion. RESULTS: Ten out of 10 MI-allergic subjects developed positive reactions to the soap with 100 ppm and seven out of nine reacted to the 50 ppm soap, while none of the 19 controls had a positive reaction during 21 days of application. No reactivity was seen to the soap without MI. The difference in reactivity to MI between MI-allergic subjects and controls was statistically significant (Fisher's exact test, P ˂ 0.0001). CONCLUSIONS: Rinse-off products preserved with 50 ppm MI or more are not safe for consumers. No safe level has yet been identified.

Methylisothiazolinone contact allergy: a review.

In the early 2000s the preservative methylisothiazolinone (MI) was released as an individual preservative for industrial products and, in 2005, it was permitted for use in cosmetic products. Up until then MI had been used only in combination with methylchloroisothiazolinone (MCI). MCI/MI is one of the most frequent causes of preservative contact allergy and early studies showed that both MI and MCI are sensitizers. The prevalence of MI contact allergy is already around 1·5% and sources of exposure are associated with occupation, cosmetic products or household products. Use of MI in industrial products is not restricted and cases of occupational contact allergy to MI, e.g. in painters, are reported. The frequency of use of MI in cosmetics is low, around 1%, while up to 16·5% of household products were preserved with MI. We found 19 (1·5%) out of 1272 cosmetic products labelled with MI, primarily rinse-off products, and analysed the concentration of MI by high-performance-liquid-chromatography the ultraviolet and mass spectrometry detection. The use concentration ranged between 2 and 100 ppm. Repeated exposure to MI showed that many patients allergic to MI reacted to 50 ppm which is half the maximum permitted concentration of MI in cosmetics. The recent cases and prevalence studies on MI contact allergy could be the first sign of an epidemic of MI contact allergy. The development in prevalence of MI contact allergy should be closely monitored by including MI in the European Baseline Series at 2000 ppm.

Low-level efficacy of cosmetic preservatives.

Preservation using combinations of preservatives has several advantages. This study shows that the concentration of some of the most frequently used allergenic preservatives can be markedly lowered when they are combined with phenoxyethanol. The antimicrobial efficacy of cosmetic preservatives and known allergens of various potency [diazolidinyl urea, methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), methylisothiazolinone (MI) and phenoxyethanol] was tested alone and in various combinations of two or three preservatives together. The preservatives were tested for minimum inhibitory concentration (MIC) values and possible synergy using fractional inhibitory concentration. MCI/MI was the only preservative showing low-level MIC against all four tested microorganisms: Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Aspergillus niger. Different combinations of the preservatives indicated additive effects against the microorganisms. No combination of preservatives showed any inhibitory action on each other. Challenge tests with different concentrations and combinations were performed in a cosmetic cream. Diazolidinyl urea and MCI/MI alone were ineffective against C. albicans in a challenge test at concentrations up to 16 times higher than the observed MIC values. When combining phenoxyethanol with either one of the allergenic preservatives diazolidinyl urea, MCI/MI or MI, the cosmetic cream was adequately preserved at concentrations well below the preservatives' MIC values as well as 10-20 times below the maximum permitted concentrations. By using combinations of preservatives, effective preservation can be achieved with lower concentrations of allergenic preservatives.

Recalls of microbiologically contaminated cosmetics in EU from 2005 to May 2008.

The Rapid Alert System for non-food consumer products in the EU (RAPEX) notifies each week the member countries on dangerous products sold in the EU. Microbiological contaminated cosmetics pose a potential health risk and are recalled from the market. This study investigated the number of recalled microbiological contaminated cosmetics products in the RAPEX database from 2005 to until week 17 in 2008. A total of 173 cosmetic products were recalled in the period, 24 were contaminated and the most frequently found micro-organism was the pathogenic Pseudomonas aeruginosa. It appears that the number of contaminated cosmetic products could be two to three times higher in 2008 compared to 2007. The recalled products were manufactured in 17 different countries and only one company had more than one product recalled. It is important to keep monitoring the cosmetic products for contamination because an increasing number of products are recalled each year, and the majority is contaminated with potential pathogenic micro-organism. More knowledge on the reasons for the contamination is needed.