A twin study of perfume-related respiratory symptoms.

Respiratory symptoms from environmental perfume exposure are main complaints in patients with multiple chemical sensitivities and often coincide with asthma and or eczema. In this population-based twin study we estimate the heritability of respiratory symptoms related to perfume and if co-occurrences of the symptoms in asthma, atopic dermatitis, hand eczema or contact allergy are influenced by environmental or genetic factors common with these diseases. In total 4,128 twin individuals (82%) responded to a questionnaire. The heritability of respiratory symptoms related to perfume is 0.35, 95%CI 0.14-0.54. Significant associations (p<0.05) between perfume-related respiratory symptoms and asthma, atopic dermatitis, hand eczema or contact allergy are not attributable to shared genetic or shared environmental/familial factors, except possibly for atopic dermatitis where genetic pleiotropy with respiratory symptoms to perfume is suggested by an estimated genetic correlation of 0.39, 95%CI 0.09-0.72.

Filaggrin null alleles are not associated with hand eczema or contact allergy.

BACKGROUND: The filaggrin protein is a key component of stratum corneum and homo- or heterozygotes for the filaggrin variant alleles R501X and 2282del4 have varying degrees of impaired skin barrier. The variant alleles have repeatedly been shown to be associated with atopic dermatitis. Any possible association with hand eczema or contact allergy are unexplored. OBJECTIVES: To explore associations between the variant alleles, hand eczema, contact allergy and atopic dermatitis. METHODS: In total, 183 adult individuals participated in a clinical examination of the hands, patch testing and filaggrin genotyping. Children without any evidence of atopic dermatitis from the Copenhagen Prospective Study on Asthma in Childhood (COPSAC) study were used as controls. The chi(2) test was used for comparison of allele frequencies. RESULTS: The majority (73%) had hand eczema, 25% had contact allergy and 14% had a diagnosis of atopic dermatitis. The association between atopic dermatitis and the filaggrin variant alleles was confirmed (odds ratio 3.5, P = 0.015). Allele frequencies in individuals with hand eczema or contact allergy were not statistically significantly increased. CONCLUSION: There is no association between the variant alleles and hand eczema or contact allergy.

Incidence of hand eczema in a population-based twin cohort: genetic and environmental risk factors.

BACKGROUND: Population-based studies on the incidence of hand eczema are sparse. OBJECTIVES: The aim of this prospective follow-up study was to determine the incidence rate of hand eczema in a population-based twin cohort. Secondly, the role of genetic factors and other potential risk factors for hand eczema was investigated. METHODS: A questionnaire on self-reported hand eczema was answered by 5610 and 4128 twin individuals in 1996 and 2005, respectively. Data were analysed in a Poisson regression analysis. RESULTS: The crude incidence rate was 8.8 cases per 1000 person-years (95% confidence interval, [CI] 7.7-9.9). Incidence rate ratios (IRRs) dependent on the co-twin's hand eczema status revealed a significant, doubled risk for monozygotic twin individuals with a co-twin affected by hand eczema, compared with dizygotic twin individuals with a co-twin affected by hand eczema (IRR 2.4, 95% CI 1.4-4.1). Also, significantly increased IRRs were found for positive patch test, atopic dermatitis, and wet work. CONCLUSIONS: Hand eczema is still a frequent disease and genetic factors are confirmed important risk factors. Positive patch test, atopic dermatitis and wet work were associated with an increased risk, whereas no association with age, sex, smoking or alcohol was found.