Background: Contact allergy is frequent among persons with hand eczema and may be associated with a poor prognosis. Objectives: To identify allergens associated with the most severe initial clinical symptoms and the worst prognosis in a cohort of hand eczema patients followed for 6 months. Methods: The study population comprised 799 consecutive hand eczema patients enrolled during January 2006–February 2007. All patients were patch tested with the European baseline series. Severity assessment of the hand eczema was performed initially and at the 6-month follow-up using a validated scoring system (HECSI). With logistic regression analyses, associations of severe hand eczema or a poor prognosis with 15 individual allergens were analysed and adjusted for by sex, age, atopic dermatitis and other allergens. Results: At baseline, greater severity of hand eczema was associated with a positive patch test to formaldehyde, methyldibromo glutaronitrile, sesquiterpene lactone mix, nickel sulfate and potassium dichromate. A poor prognosis was associated with chromate allergy, odds ratio: 4.18 (95% CI: 1.42–12.28). Conclusions: Nickel, chromate, formaldehyde, methyldibromo glutaronitrile and sesquiterpene lactone mix were allergens associated with the greatest severity of hand eczema. Patients with chromate allergy had the worst prognosis. [ABSTRACT FROM AUTHOR]