Occupational contact dermatitis is a common issue, and hairdressing is one of the most frequently affected professions. Hairdressers endure prolonged exposure to water, along with allergens potentially present in hair dyes, bleaching agents, styling products, and even protective gloves. Estimates show that hairdressers have over twice the incidence of hand eczema (HE) compared to the general population, with cumulative lifetime prevalence ranging from 29.1% to 42.3%.

Occupational hand eczema (OHE) often has a negative impact on work. Most hairdressers exhibit early onset of HE, so it's unsurprising that HE-related dropout rates are high among hairdressing apprentices. Studies report that nearly half of hairdressers have left the profession, with 23.1% citing HE as their reason for quitting. Currently, our understanding of the long-term course of HE in hairdressers is poor, and the need for primary prevention later in their careers remains unclear.

We conducted a prospective cohort study of trained hairdressers established in 2009, who graduated between 1985-2007 and were followed up in 2020. We assessed the prevalence and incidence of HE and its associated risk factors, as well as the prognosis for hairdressers who reported HE at baseline.

Methods: A prospective cohort study included all hairdressers graduating from Danish hairdressing vocational schools between 1985-2007. A self-administered questionnaire was distributed in 2009 with follow-up in 2020. Data from Denmark's Labor Market Supplementary Pension Scheme provided annual information on affiliation with the hairdressing industry.

Results: The lifetime cumulative prevalence of HE increased from 42.3% at baseline to 45.2% at follow-up (odds ratio [OR] 1.1; 95% CI 1.0-1.2). Incidence decreased from 42.8 cases/1000 person-years (95% CI 40.8-44.8) at baseline to 3.4 cases/1000 person-years (95% CI 2.5-4.6) during follow-up. Over 90% of cases developed within 8 years of starting apprenticeship, with 68% occurring during the apprenticeship period. Risk factors associated with HE at baseline included prior positive patch test (adjusted OR [AOR] 5.3; 95% CI 4.2-6.6), history of atopic dermatitis (AOR 3.4; 95% CI 2.9-4.0), and female sex (AOR 1.8; 95% CI 1.4-2.3). At follow-up, the most significant risk factors were prior HE (AOR 10.1; 95% CI 7.3-13.8) and positive patch test during follow-up (AOR 4.5; 95% CI 3.0-6.8). Among hairdressers with HE at baseline, 65.5% showed remission at follow-up, while 34.6% had persistent and often severe HE. Those with persistent HE represented the subgroup most consistently affected by HE risk factors in the study population.

In this study, we conducted a follow-up survey of hairdressers for up to 35 years after graduation. We observed a slight increase in the lifetime prevalence of HE, rising from 42.3% at the 2009 baseline to 45.2% at the 2020 follow-up. The incidence rate ratio (IRR) for first-onset HE in hairdressers was 0.08 when comparing the period from graduation to baseline with the period from baseline to follow-up. This indicates that the incidence of HE has nearly completely ceased. Additionally, over 90% of hairdressers experienced an HE episode by the eighth year of their career, with 63.1% of hairstylists first developing HE during their apprenticeship. Our data suggest that new-onset HE in hairdressers is primarily associated with apprenticeship and the initial years of professional work.

The main risk factor for HE during follow-up was previous HE, highlighting the need for early primary prevention. Overall improvement in HE was evident, but notably, 34.6% of hairdressers with HE suffered from persistent dermatitis, often severe. This equates to 14.2% of the study population, indicating that a significant portion of graduates remain affected years after graduation. Graduates with persistent HE were more likely to be female, have a history of atopic dermatitis (AD), or show positive patch test results, underscoring the importance of these risk factors for HE. Interestingly, there was no significant difference in the number of years working as a hairdresser between those with and without a history of AD. This suggests that excessive exposure to hairdressing irritants and allergens quickly exceeds the threshold for contact dermatitis even in individuals with normal skin barrier function. While hairdressers with a history of AD are more likely to develop HE and thus require occupational guidance, early primary prevention appears equally important for apprentices regardless of their atopic predisposition.

Primary prevention of HE should focus on newly graduated hairdressing apprentices and trained hairdressers. Approximately one-third of hairdressers develop persistent, severe HE, emphasizing the need for early intervention.