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Dermatitis And Allergies To Cosmetic Ingredients

Dermatitis And Allergies To Cosmetic Ingredients


In the realm of hair cosmetics, a plethora of products harbor various potent contact allergens, including additives such as preservatives. This concern is particularly pronounced among individuals involved in hairdressing, who frequently manifest hand dermatitis. Furthermore, clients and self-users, hereafter referred to as ‘consumers,’ may exhibit severe dermatitis on the scalp and face.


The objective of this study was to discern disparities in sensitization frequencies to hair cosmetic components and other select allergens between female subjects undergoing patch testing, differentiating between hairdressers and consumers without professional backgrounds. These individuals were tested for suspected allergic contact dermatitis stemming from the utilization of such products.


The investigation involved a descriptive analysis of patch test data and clinical information gathered by the Information Network of Departments of Dermatology (IVDK) during the period from January 2013 to December 2020. The primary focus of the analysis was on age-adjusted sensitization prevalences within the two distinct subgroups.


The results of this inquiry, encompassing 920 hairdressers (median age: 28 years, with 84% presenting hand dermatitis) and 2321 consumers (median age: 49 years, with 71.8% exhibiting head/face dermatitis), revealed notable insights. Sensitization to p-phenylenediamine exhibited age-standardized prevalence rates of 19.7% among hairdressers and 31.6% among consumers, while toluene-2,5-diamine showed rates of 20% and 30.8%, respectively. Remarkably, consumers displayed a higher incidence of contact allergies to other oxidative hair dye ingredients. Conversely, ammonium persulphate (14.4% vs. 2.3%), glyceryl thioglycolate (3.9% vs. 1.2%), and notably, methylisothiazolinone (10.5% vs. 3.1%) were more frequently identified allergens among hairdressers.


Hair dyes emerged as the predominant sensitizers among both hairdressers and consumers. However, it is essential to recognize that the prevalence rates may not be directly comparable, as the criteria for patch testing can vary. This underscores the significance of addressing hair dye allergies, often compounded by reactivity. It is imperative to further enhance workplace safety and product standards in this domain of cosmetics.



Hairdressers routinely face exposure to a range of irritants and potent allergens, often without adequate protection. This occupational hazard frequently results in hand eczema, which may stem from irritant causes, contact allergies, or a combination of both. Hand eczema can lead to sick leave and, in severe cases, job loss. Recent systematic reviews have shed light on the burden of morbidity among hairdressers, focusing on cosmetic ingredients’ implications, respiratory and systemic exposure, and associated toxicological effects, as well as contact allergies related to key hair cosmetic components. In contrast, clients of hairdressers and individuals who apply hair cosmetics themselves, collectively referred to as ‘consumers,’ are less susceptible to irritant contact dermatitis due to less frequent skin contact with these products. However, they can still develop allergic contact dermatitis if they become sensitized to an ingredient within the cosmetics.

Several national contact dermatitis societies and suppliers of patch test allergens maintain specialized ‘hairdresser’ or ‘hair cosmetic’ patch test series. In addition, there exists a European recommendation for such a series dating from 2015. When diagnosing hairdressers with occupational contact dermatitis or consumers with suspected allergic contact dermatitis from hair cosmetics, patch testing with this specialized series plays a pivotal role. It is typically combined with the baseline series, other relevant specialized series, or, when necessary, the patient’s own products. Continuous analysis of patch test results from the Information Network of Departments of Dermatology (IVDK) has been ongoing, covering the period from 1995 to 2012. This paper serves as a follow-up to previous analyses, employing the same methodology to provide a current evidence base. This data aids in adapting the test series and facilitates risk assessment concerning the covered ingredients.



The Information Network of Departments of Dermatology (IVDK) is a dedicated network focused on the clinical monitoring of contact allergies. It primarily comprises departments in Germany (50), followed by Switzerland (6) and Austria (3). These departments are members of the German Contact Dermatitis Research Group (DKG) and adhere to the guidelines of the European Society of Contact Dermatitis for patch testing, with some refinements. They collect patch test data, along with clinical information and patient history, which is then electronically transmitted to the data center in Göttingen for quality checks and consolidation, occurring twice a year.


The study conducted spans from January 2013 to December 2020, covering a total of 92,898 consultations, of which 58,498 (63%) were by female patients. Among female patients, two distinct subgroups were identified:


  1. Hairdressers: Comprising females who were either currently working as hairdressers and diagnosed with occupational dermatitis or had previously experienced occupational dermatitis while working as hairdressers (totaling 920 individuals).
  2. Consumers: Encompassing female patients in whom hair cosmetics were suspected as the cause of contact dermatitis. They had never worked as hairdressers but had utilized hair cosmetic products themselves or had them applied by non-professional helpers. This group also included clients of hairdressing salons (totaling 2,321 individuals).


A descriptive comparison was conducted between these two subgroups concerning demographic and clinical characteristics. Additionally, the prevalence of sensitization to allergens included in the ‘hairdresser series’ of the DKG was examined. Sensitization to preservatives and other constituents that might be found in hair cosmetics, tested as part of the baseline or other special test series, was also analyzed.


Patch test preparations were sourced from specific suppliers, and readings were taken on either the third day (D3) or fourth day (D4) after the application of patches. Results were categorized as ‘positive’ (including +, ++, and +++ reactions) or ‘non-positive’ (comprising doubtful, irritant, and negative reactions). When re-consultations occurred (noted in 2% of cases) with patch testing for the same allergen(s), a positive reaction took precedence over a non-positive one (referred to as the ‘believe-the-positive’ approach).


Prevalence estimates were age-standardized, taking into account individuals aged under 40 and those aged 40 and above. Statistical tests were applied to identify differences, heterogeneity, trends, and asymmetry in cross-reactivity assessments. Logistic regression analysis was employed to quantify the impact of various factors on the observed outcomes.


This study examined data from 3,241 female patients and analyzed important demographic and clinical information. The study spanned eight years, and a decrease in the number of patch tests in the most recent years was observed, which coincided with the impact of the COVID-19 pandemic on patient care in 2020. Even without considering the pandemic year, a significant downward trend in patient numbers was noted. Hairdressers were notably younger than consumers, and the primary affected sites differed significantly, with hairdressers predominantly experiencing hand involvement, while consumers had more facial, head, and neck dermatitis.


Around 90% of patients in both subgroups were tested with baseline and hairdresser series, but the cosmetic preservatives series was tested more frequently in hairdressers (almost 80%) compared to consumers (two-thirds).


The primary intermediates of oxidative hair dyes, toluene-2,5-diamine (PTD) and p-phenylenediamine (PPD), were the leading allergens in both hairdressers and consumers. Consumers exhibited a higher sensitization prevalence to these allergens, approximately 50% more. Cross-reactivity was also observed between these substances and related compounds, such as p-aminophenol and hydroxyethyl-PPD (HE-PPD), though isolated reactions to HE-PPD were rare.


Secondary intermediates or couplers, such as 4-amino-2-hydroxytoluene, m-aminophenol, and 2-methylresorcinol, showed varying sensitization frequencies. Hydroquinone and pyrogallol, no longer permitted in cosmetic products in the EU, still elicited allergic reactions, primarily in young consumers. Sensitization to these substances was more prevalent in young individuals.


Regarding ingredients in bleaches and waving products, ammonium persulphate (APS) was more commonly allergenic in hairdressers compared to consumers, with glyceryl thioglycolate (GMTG) also showing a higher prevalence in hairdressers, except for cysteamine hydrochloride, which was a rare sensitizer.


Preservatives, specifically methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI)/MI, demonstrated a threefold higher prevalence in sensitization among hairdressers compared to consumers. Other preservatives showed negligible differences.


Overall, this study sheds light on the sensitization patterns in hairdressers and consumers to various hair cosmetic ingredients and highlights the differential responses to allergens in these groups.



This analysis is the fourth of its kind and follows a similar methodology, providing an updated overview of contact allergy prevalences in specific clinical samples. The study focuses on two distinct groups: hairdressers, predominantly young females with hand eczema, and consumers, mainly older women with scalp and facial dermatitis. Hairdressers often use hair cosmetics on themselves and are potentially at risk of scalp, face, or neck dermatitis.


The study reveals that contact allergy to hair dye product ingredients is more common in consumers compared to hairdressers, potentially due to the widespread use of hair dyes, which are popular even among adolescents. However, some differential selection processes may also contribute to these variations, such as the healthy worker effect in hairdressers.


Bleaching procedures are primarily performed in salons, while waving and straightening procedures are not typically done at home due to their complexity. Sensitization to the perming allergen glyceryl thioglycolate (GMTG) appears to occur sporadically and inconsistently, with minimal consistent patterns observed.


Among the ingredients, cocamidopropyl betaine (CAPB) has low allergenicity, even among a highly selective sample. However, sensitization to CAPB may be related to impurities or irritant reactions, requiring cautious interpretation of positive results.


Preservatives, including methylisothiazolinone (MI), methylchloroisothiazolinone (MCI/MI), and methyldibromo glutaronitrile (MDBGN), are overrepresented in hairdressers. MI has been banned from leave-on cosmetics in the EU but is still used in rinse-off products, possibly posing risks for sensitized hairdressers. This could be due to inadequate protection of hairdressers’ hands during wet work without gloves.


Some newly added coupling agents, such as 4-amino-2-hydroxytoluene, elicited many positive reactions, while 2-methylresorcinol was a rare allergen. Cross-reactivity between PPD and PTD was observed with HE-PPD, and caution is advised when considering 4-amino-2-hydroxytoluene as an independent sensitizer.


The study emphasizes the differences in sensitization patterns between hairdressers and consumers, with potential variations in selection processes and exposure levels. Extrapolating sensitization risks to consumers remains challenging due to limited exposure and disease data, but hairdressers may consult dermatologists more readily and get patch tested due to potential occupational consequences. However, these notions require further empirical confirmation.


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