**2.1 Gender and age**

Women are usually more frequently patch-tested, and have more positivity results than men (García-Gavín et al, 2011). Gender differences may be attributed to social and environmental factors; females are more likely to have nickel sensitivity because of increased wearing of jewellery, and males are more likely to have chromate sensitivity from occupational exposure (Ruff & Besilto, 2006).

Epidemiology of Contact Dermatitis 5

and abrasives. ACD is a common skin condition that can be difficult to diagnose without the aid of a specific diagnostic tool called patch testing. Patch testing performed with a relevant panel of contact allergens is the ultimate confirmatory test of ACD (see Chapter titled "Allergens (patch test studies) from the European Baseline Series" on this book). Correctly

General population studies have repeatedly found that atopic dermatitis is the most important risk factor for hand eczema (Meding & Swanbeck, 1990; Dotterud & Falk, 1995; Yngveson M et al, 2000; Mortz et al, 2001; Meding & Jarvholm, 2002; Bryld et al, 2003; Josefson et al, 2006). Thus, the effect of atopic dermatitis seemed to level off with increasing age. Whether association between hand eczema on the one hand and atopic dermatitis or atopy on the other hand is explained by null mutations in the filaggrin gene (de Jongh et al, 2008; Carlsen et al, 2011), by an altered immune response (Davis et al, 2010; McFadden et al, 2011), or by their combination is currently unknown. Future studies should aim to

Studies have re-investigated a possible association between these lifestyle factors (alcohol

A substantial number of studies have also investigated the prevalence of contact allergy in the general population and in unselected subgroups of the general population (Thyssen et al, 2007). These studies have demonstrated variations in the prevalence of contact allergy depending on the selected study population and year of investigation. These studies are of high value as they tend to be less biased than studies using clinical populations and as they are important for health care decision makers when they allocate resources. Literature was examined using Pubmed-Medline, Biosis, Science Citation Index, and dermatology text books. Search terms included hand eczema, hand dermatitis, general population, unselected, healthy, prevalence, incidence, risk factor, and epidemiology. In observational studies on contact dermatitis, the ascertainment of cases varied from intensive efforts by a medical examination of the complete study population to the relatively easy-to-apply method of self-administered questionnaires; or by a combination of both. However, a diagnosis of contact dermatitis based on a self-administered questionnaire is significantly less valid than the diagnosis based on examination by a

Information on the prevalence of hand eczema, contact sensitivity and contact dermatitis in the general population can be obtained from cross-sectional studies that were performed recently (Thyssen et al, 2009; Nielsen et al, 2001a, 2001b; Mortz et al, 2001;

drinking and tobacco smoking) and contact sensitization (Thyssen et al, 2010).

identifying the inciting allergen permits appropriate personal avoidance.

**2.4 Personal history of atopic dermatitis** 

investigate the distribution of these risk factors.

**2.5 Other possible association** 

dermatologist (McCurdy et al, 1989).

**3. Hand eczema in the general population** 

**2.6 Analyzed literature** 

Rui et al estimate the prevalence of nickel, cobalt and chromate allergy in a population of consecutive patients and investigate the possible association with individual and occupational risk factors (Rui et al, 2010). This study showed interesting associations between some occupations and nickel, chromate and cobalt allergy.

ACD in children, until recently, was considered rare (Hammonds et al, 2009). One of the largest population-based patch test studies of unselected pediatric patients, which also provides specific relevance information, found the prevalence of past or current relevant reactions to be 7%, with a higher risk seen in females (Mortz et al, 2002). This is considerably lower than the prevalence in selected pediatric populations (symptomatic patients). Nickel is the most common sensitizer in almost all studies pertaining to pediatric contact dermatitis. Thus, the real prevalence of ACD (defined as a positive patch test with clinical correlation with the dermatitis experienced by a symptomatic individual) ranges from 14% to 77% among children referred for patch testing due to clinical suspicion of contact dermatitis (Bruckner et al, 2000; Fernández Vozmediano & Armario Hita, 2005; Seidenari et al, 2005; Lewis et al, 2004).

Eczema in adults usually exists for years, compromising quality of life and occupational choices. The flexural areas, shoulders, head-and-neck, and hands are typically affected in 5- 15% of cases (Katsarou et al, 2001). The relationship between atopy and contact allergy remains unclear. Atopic dermatitis is a risk factor for allergic contact sensitization (Dotterud & Smith-Sivertsen, 2007). ACD increases with age in atopics (Lammintausta et al, 1992).

Contact dermatitis is a significant health problem affecting the elderly people. Impaired epidermal barrier function and delayed cutaneous recovery after injury enhances susceptibility to both irritants and allergens. Exposure to more numerous potential sensitizers and for greater durations influences the rate of allergic contact dermatitis in this population. Medical co-morbidities, including stasis dermatitis and venous ulcerations, further exacerbate this clinical picture (Prakash & Davis, 2010). Aging is correlated with the rate and type of contact sensitization, but only a few studies have evaluated patch test reactivity in elderly individuals with an adequately large population (Nedorost & Stevens, 2001; Balato et al, 2011).

#### **2.2 Race**

Black people may be less susceptible to sensitisation by weaker allergens and have a lower incidence of ICD because of greater compaction of the lipid component of the stratum corneum, conferring improved barrier function (Robinson, 1999; Astner et al, 2006). Ethnicity is a possible endogenous factor implicated in ICD. While there is a clinical consensus that blacks are less reactive and Asians are more reactive than Caucasians, the data supporting this hypothesis rarely reaches statistical significance. Modjtahedi SP et al conclude that race could be a factor in ICD, which has practical consequences regarding topical product testing requirements, an ever-expanding global market, occupational risk assessment, and the clinical thinking about ICD (Modjtahedi & Maibach, 2002).

#### **2.3 Exposure to irritants and allergens**

The most important risk factor for OCD is the exposure to irritants. Well-known irritants are water (wet work), detergents and cleansing agents, hand cleaners, chemicals, cutting fluids,

Rui et al estimate the prevalence of nickel, cobalt and chromate allergy in a population of consecutive patients and investigate the possible association with individual and occupational risk factors (Rui et al, 2010). This study showed interesting associations

ACD in children, until recently, was considered rare (Hammonds et al, 2009). One of the largest population-based patch test studies of unselected pediatric patients, which also provides specific relevance information, found the prevalence of past or current relevant reactions to be 7%, with a higher risk seen in females (Mortz et al, 2002). This is considerably lower than the prevalence in selected pediatric populations (symptomatic patients). Nickel is the most common sensitizer in almost all studies pertaining to pediatric contact dermatitis. Thus, the real prevalence of ACD (defined as a positive patch test with clinical correlation with the dermatitis experienced by a symptomatic individual) ranges from 14% to 77% among children referred for patch testing due to clinical suspicion of contact dermatitis (Bruckner et al, 2000; Fernández Vozmediano & Armario Hita, 2005;

Eczema in adults usually exists for years, compromising quality of life and occupational choices. The flexural areas, shoulders, head-and-neck, and hands are typically affected in 5- 15% of cases (Katsarou et al, 2001). The relationship between atopy and contact allergy remains unclear. Atopic dermatitis is a risk factor for allergic contact sensitization (Dotterud & Smith-Sivertsen, 2007). ACD increases with age in atopics (Lammintausta et al, 1992).

Contact dermatitis is a significant health problem affecting the elderly people. Impaired epidermal barrier function and delayed cutaneous recovery after injury enhances susceptibility to both irritants and allergens. Exposure to more numerous potential sensitizers and for greater durations influences the rate of allergic contact dermatitis in this population. Medical co-morbidities, including stasis dermatitis and venous ulcerations, further exacerbate this clinical picture (Prakash & Davis, 2010). Aging is correlated with the rate and type of contact sensitization, but only a few studies have evaluated patch test reactivity in elderly individuals with an adequately large population (Nedorost & Stevens,

Black people may be less susceptible to sensitisation by weaker allergens and have a lower incidence of ICD because of greater compaction of the lipid component of the stratum corneum, conferring improved barrier function (Robinson, 1999; Astner et al, 2006). Ethnicity is a possible endogenous factor implicated in ICD. While there is a clinical consensus that blacks are less reactive and Asians are more reactive than Caucasians, the data supporting this hypothesis rarely reaches statistical significance. Modjtahedi SP et al conclude that race could be a factor in ICD, which has practical consequences regarding topical product testing requirements, an ever-expanding global market, occupational risk

The most important risk factor for OCD is the exposure to irritants. Well-known irritants are water (wet work), detergents and cleansing agents, hand cleaners, chemicals, cutting fluids,

assessment, and the clinical thinking about ICD (Modjtahedi & Maibach, 2002).

between some occupations and nickel, chromate and cobalt allergy.

Seidenari et al, 2005; Lewis et al, 2004).

2001; Balato et al, 2011).

**2.3 Exposure to irritants and allergens** 

**2.2 Race** 

and abrasives. ACD is a common skin condition that can be difficult to diagnose without the aid of a specific diagnostic tool called patch testing. Patch testing performed with a relevant panel of contact allergens is the ultimate confirmatory test of ACD (see Chapter titled "Allergens (patch test studies) from the European Baseline Series" on this book). Correctly identifying the inciting allergen permits appropriate personal avoidance.

#### **2.4 Personal history of atopic dermatitis**

General population studies have repeatedly found that atopic dermatitis is the most important risk factor for hand eczema (Meding & Swanbeck, 1990; Dotterud & Falk, 1995; Yngveson M et al, 2000; Mortz et al, 2001; Meding & Jarvholm, 2002; Bryld et al, 2003; Josefson et al, 2006). Thus, the effect of atopic dermatitis seemed to level off with increasing age. Whether association between hand eczema on the one hand and atopic dermatitis or atopy on the other hand is explained by null mutations in the filaggrin gene (de Jongh et al, 2008; Carlsen et al, 2011), by an altered immune response (Davis et al, 2010; McFadden et al, 2011), or by their combination is currently unknown. Future studies should aim to investigate the distribution of these risk factors.

#### **2.5 Other possible association**

Studies have re-investigated a possible association between these lifestyle factors (alcohol drinking and tobacco smoking) and contact sensitization (Thyssen et al, 2010).

#### **2.6 Analyzed literature**

A substantial number of studies have also investigated the prevalence of contact allergy in the general population and in unselected subgroups of the general population (Thyssen et al, 2007). These studies have demonstrated variations in the prevalence of contact allergy depending on the selected study population and year of investigation. These studies are of high value as they tend to be less biased than studies using clinical populations and as they are important for health care decision makers when they allocate resources. Literature was examined using Pubmed-Medline, Biosis, Science Citation Index, and dermatology text books. Search terms included hand eczema, hand dermatitis, general population, unselected, healthy, prevalence, incidence, risk factor, and epidemiology. In observational studies on contact dermatitis, the ascertainment of cases varied from intensive efforts by a medical examination of the complete study population to the relatively easy-to-apply method of self-administered questionnaires; or by a combination of both. However, a diagnosis of contact dermatitis based on a self-administered questionnaire is significantly less valid than the diagnosis based on examination by a dermatologist (McCurdy et al, 1989).

#### **3. Hand eczema in the general population**

Information on the prevalence of hand eczema, contact sensitivity and contact dermatitis in the general population can be obtained from cross-sectional studies that were performed recently (Thyssen et al, 2009; Nielsen et al, 2001a, 2001b; Mortz et al, 2001;

Epidemiology of Contact Dermatitis 7

up studies, selection of subjects is based upon exposure to the factor of interest. Instead of exposure, the presence or absence of a risk factor (e.g. nickel allergy, or atopy) can also be chosen as basis for comparison. In case-control studies, the subjects are selected according to their disease status. Information on the past exposure of the persons with contact dermatitis (cases) and the non-diseased persons (controls) is collected. In cross-sectional studies, a study population is selected regardless of exposure status or disease status (in contrast to

Data on the incidence and prevalence of occupational dermatoses are scarce. The most important sources of data are occupational disease registries, case series of patients visiting dermatology clinics, and a limited number of cross-sectional studies in one or more

*Incidence of hand eczema:* Several studies have investigated the incidence of hand eczema in the general population (Lantinga et al, 1984; Yngveson M, 2000; Meding & Jarvholm, 2004; Brisman J et al, 1998; Meding et al, 2006; Lind, 2007; Lerbaek et al, 2007). The median incidence rate was 5.5 cases/1000 person-years (range 3.3–8.8). Stratified by sex, the median incidence rate of hand eczema was 9.6 cases/1000 person-years (range 4.6–11.4) among women and 4.0 cases/1000 person-years (range 1.4–7.4) among men (Thyssen et al,

*Prevalence of hand eczema:* Few studies showed that the 1-year median prevalence of hand eczema in the general population was 9.7% (11.4% among women and 5.4% among men) and that the 1-year weighted average prevalence was 9.1% (10.5% among women and 6.4% among men) (Lantinga et al, 1984; Agrup, 1969; Peltonen, 1979; Menné et al, 1982; Kavli & Forde, 1984; Meding, 1990; Meding & Swanbeck, 1987; Meding & Jarvholm, 2002; Ortengren, 1999; Meding et al, 2001; Brisman J et al, 1998; Montnemery et al, 2005; Bo et al, 2008; Fowler

Population studies may give valuable information on the magnitude of the disease problem. Different data was found when compared the frequencies of positive path-tests reactions in the general population and in eczema patients at a dermatological clinic in the same area (Menné & Knudsen 1997) (Table 1). Publications based on data of patients visiting dermatology clinics and/or patch testing units can not be used to directly derive population related incidence or prevalence estimates. Data from incidence studies may support and direct strategies for the prevention of contact allergy and ACD, supporting conclusions

Nickel sulphate is the most common allergen in the standard series and the most common cause of allergic contact dermatitis, particularly in women. This gender difference is traditionally explained by increased exposure in women, due to direct skin contact with nickel-releasing metal, such as in jewellery, wristwatches, and clothing accessories. A possible association between nickel allergy and hand eczema in women has been addressed and supported by several population-based studies, whereas an association has been questioned in men (Nielsen et al, 2002; Peltonen, 1979; Meijer et al, 1995) (Tables 2

**3.3 Incidence and prevalence of contact dermatitis and contact sensitisation** 

et al, 2006; Hald et al, 2008; Svedman et al, 2007; Lind et al, 2007).

derived from clinical surveillance data.

case-control and follow-up studies).

occupational groups.

2010).

and 3).

Sosted et al, 2005; Lerbaek et al, 2007). Several studies have investigated the incidence of hand eczema in the general population (Bo et al, 2008; Hald et al, 2008; Moberg et al, 2009; Lind et al, 2007).

Hand eczema is the most frequent occupational skin disease. In many jobs the skin on the hands is subjected to damage caused by contact with skin irritants and contact allergens. Several studies have investigated the incidence and prevalence of hand eczema in the general population.
