Jeanne D. Johansen

The epidemiology of contact allergy in the general population--prevalence and main findings.

A substantial number of studies have investigated the prevalence of contact allergy in the general population and in unselected subgroups of the general population. The aim of this review was to determine a median prevalence and summarize the main findings from studies on contact allergy in the general population. Published research mainly originates from North America and Western Europe. The median prevalence of contact allergy to at least 1 allergen was 21.2% (range 12.5–40.6%), and the weighted average prevalence was 19.5%, based on data collected on all age groups and all countries between 1966 and 2007. The most prevalent contact allergens were nickel, thimerosal, and fragrance mix. The median nickel allergy prevalence was 8.6% (range 0.7–27.8%) and demonstrates that nickel was an important cause of contact allergy in the general population and that it was widespread in both men and women. Numerous studies demonstrated that pierced ears were a significant risk factor for nickel allergy. Nickel was a risk factor for hand eczema in women. Finally, heavy smoking was associated with contact allergy, mostly in women. Population‐based epidemiological studies are considered a prerequisite in the surveillance of national and international contact allergy epidemics.

Contamination versus preservation of cosmetics: a review on legislation, usage, infections, and contact allergy

Cosmetics with high water content are at a risk of being contaminated by micro‐organisms that can alter the composition of the product or pose a health risk to the consumer. Pathogenic micro‐organisms such as Staphylococcus aureus and Pseudomonas aeruginosa are frequently found in contaminated cosmetics. In order to avoid contamination of cosmetics, the manufacturers add preservatives to their products. In the EU and the USA, cosmetics are under legislation and all preservatives must be safety evaluated by committees. There are several different preservatives available but the cosmetic market is dominated by a few preservatives: parabens, formaldehyde, formaldehyde releasers, and methylchloroisothiazolinone/methylisothiazolinone.

The association between null mutations in the filaggrin gene and contact sensitization to nickel and other chemicals in the general population

Background  It was recently shown that filaggrin gene (FLG) null mutations are positively associated with nickel sensitization. We have hypothesized that histidine‐rich filaggrin proteins in the epidermis chelate nickel ions and prevent their skin penetration and exposure to Langerhans cells. Furthermore, we have proposed that the low degree of genetic predisposition to nickel sensitization found by a Danish twin study was explained by a high prevalence of ear piercing among participants resulting in ‘bypassing’ of the filaggrin proteins.

Contact allergy epidemics and their controls

Contact dermatitis can be severe and lead to sick leave as well as significant healthcare expenses. The aim of this review is to present the published knowledge on 6 historical epidemics of contact allergy to apply this knowledge on the prevention and control of future contact allergy epidemics. A historical review is performed on nickel, chromium, methylchloroisothiazolinone/methylisothiazolinone, methyldibromo glutaronitrile, formaldehyde, and para‐phenylenediamine. The first cases of contact dermatitis are mostly occupational, whereas consumer cases appear later. There is often a latency period from the first cases are observed until an epidemic occurs, and the problem is recognized. Finally, no one seems to take responsibility of dealing with the situation, and there are no attempts of regulation until an epidemic is consolidated among consumers for many years. Steps should be taken to prevent contact allergy epidemics. It is essential that dermatologist, scientists, administrators, and consumers organize and structure known methods to accelerate the control of emerging contact allergens.

Contact sensitization to common haptens is associated with atopic dermatitis: new insight

Background  It has been much debated whether atopic dermatitis (AD) is associated with contact sensitization as past findings have been conflicting. A positive association might change our clinical practice.

Prevalence and cause of methylisothiazolinone contact allergy.

Background: Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) has been one of the most frequent sensitizers since the 1980s. In 2005, the use of MI alone was approved for the preservation of cosmetic and household products in the EU. Before that, MI was used in industrial products, and the first cases of isolated MI contact allergy were published.

Filaggrin null mutations increase the risk and persistence of hand eczema in subjects with atopic dermatitis: results from a general population study

Summary Background  Hand eczema is prevalent in the general population. It remains unclear whether or not filaggrin gene (FLG) null mutations increase the overall risk of hand eczema or only increase the risk of hand eczema in subjects with atopic dermatitis.

Contact allergy to the 26 specific fragrance ingredients to be declared on cosmetic products in accordance with the EU cosmetics directive

Background. Fragrance ingredients are a frequent cause of allergic contact dermatitis. The EU Cosmetics Directive states that 26 specific fragrance ingredients, known to cause allergic contact dermatitis, must be declared on the ingredient lists of cosmetic products.

Contact allergy and allergic contact dermatitis in children - a review of current data.

Allergic contact dermatitis (ACD) in children was previously considered to be a rare occurrence. However, the growing number of case reports and cross‐sectional studies through the past three decades indicate that ACD is, in fact, a highly relevant diagnosis in children. Furthermore, the frequency of ACD in children seems to be increasing. In 1999, a review of the literature reported prevalence rates of 14.5–70% in selected paediatric populations. The current paper reviews the studies on the prevalence of positive patch test reactions and ACD in the paediatric population during the past decade, and provides an overview of the main findings. We found reported sensitization rates of 26.6–95.6% in selected groups of children. The associated relevance was 51.7–100%. The most common allergens were nickel, cobalt, thimerosal, and fragrance. Tailored patch testing increases the rate of relevant patch test reactions. Children with atopic dermatitis are as frequently sensitized as children with no history of atopic dermatitis, and there are no differences associated with sex. Children and adults can be tested with equal concentrations of patch test allergens. Our findings may support the notion that the prevalence of ACD in children is increasing over time or indicate an increased awareness.

20 Years of standard patch testing in an eczema population with focus on patients with multiple contact allergies

Results of standard patch tests performed with the same methodology in one centre are rarely available over a large time span. This gives the unique opportunity to study not only prevalence but also persistency of contact allergy and characterize subpopulations. The objectives were to investigate sensitivity rates and persistencies of patch test results and characterize patients with multiple contact allergies. A 20‐year retrospective database‐based study of 14 998 patients patch tested with the European Standard Series was performed. 34.5% were sensitized, primarily women. Sensitivity to nickel was most frequent and least frequent to mercaptobenzothiazole, N‐isopropyl‐N‐phenyl‐p‐phenylenediamine and benzocaine. Yearly proportion of negative, mono/double‐allergic, and multiple‐allergic cases remained stable. Persistency of positive reactions was high for para‐phenylenediamine, Cl(Me)isothiazolinone, and primin and poor for paraben mix. 5.1% were multiple allergic, primarily women, and 90% got diagnosed by the first test. Frequency of multiple allergies increased with age. More multiple‐ than mono/double‐allergic patients were tested multiple times. Persistency and sensitivity rates in a Danish eczema population are provided and are useful for decisions regarding the standard series. Patients with multiple contact allergies are typically elderly women who might have long‐lasting and hard‐to‐treat eczema. Cumulative environmental exposure seems necessary to develop multiple allergies.