The association between contact sensitization and atopic disease by linkage of a clinical database and a nationwide patient registry

Background Experimental studies have shown that individuals with atopic dermatitis are likely to have suppressed contact sensitivity secondary to their disease whereas some clinical and epidemiological studies have shown that individuals with atopic dermatitis might have a higher prevalence of contact sensitization than controls. The objective was to study the association between contact sensitization and, respectively, atopic dermatitis and asthma using clinical databases. Methods Record linkage of two different registers was performed: (i) a tertiary hospital register of dermatitis patient's patch tested for contact sensitivity and (ii) the Danish National Patient Register containing nationwide hospital discharge diagnoses and outpatient contacts. Results An inverse association was found between contact sensitization and, respectively, presumed severe atopic dermatitis (OR, 0.70; 95% CI, 0.610.81) and asthma (OR, 0.61; 95% CI, 0.420.90) when linkage was performed. Inverse associations were found for all groups of chemicals and metals except for sensitization to fragrances and topical drugs where positive associations were identified. A significant positive association between fragrance sensitization and presumed mildmoderate atopic dermatitis was also found when data from hospital register only were used, suggesting an overall higher prevalence of fragrance sensitization in patients with atopic dermatitis. Conclusions Our findings support that patients with severe atopic dermatitis and asthma have an overall lower prevalence of contact sensitization when compared with controls, whereas mild-to-moderate disease does not suppress contact sensitization. The prevalence of contact sensitization to fragrance chemicals was higher in patients with atopic dermatitis. Patients should be instructed to avoid scented moisturizers and products containing highly sensitizing substances.