Allergic contact dermatitis in adults with and without atopic dermatitis: Evaluation of the Spanish Contact Dermatitis Registry (REIDAC).

Background: Atopic dermatitis (AD) and allergic contact dermatitis (ACD) are inflammatory skin conditions whose association is not clearly defined.

Objectives: To identify differences in ACD profile between patients with and without AD among those referred for patch testing. Additionally, to determine the prevalence of sensitisation to standard Spanish contact allergens in both groups.

Methods: We analysed two groups (AD and non-AD) within the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy (REIDAC). Contact allergy, clinical relevance and epidemiological data were compared between them.

Results: A total of 5055 patients were included. Among them, 23% (1168) had a history or final diagnosis of AD. At least one positive reaction was seen in 468 (40%) of AD patients and 1864 (48%) of non-AD patients. In both groups, the most common positive reactions were to nickel sulphate, methylchloroisothiazolinone/methylisothiazolinone and cobalt chloride. Age-adjusted OR for sensitisation to nickel sulphate was 0.72 (95% CI: 0.61-0.86), indicating a decreased likelihood of sensitisation in AD patients compared to non-AD individuals.

Conclusions: We did not find an increased presence of ACD in patients with AD referred for patch testing, exhibiting similar profiles to non-AD population, except for a negative relationship between AD and sensitisation to nickel sulphate.