Formaldehyde.

Formaldehyde is the American Contact Dermatitis Society Contact Allergen of the Year for 2015. The exposure is widespread, and contact allergy might be difficult to suspect in the individual dermatitis patient. The relevance of contact allergy to formaldehyde might also be difficult to evaluate. Recently, however, several studies have been performed aimed at enhancing the patch test technique and evaluating the clinical relevance of contact allergy to formaldehyde. The patch test concentration of formaldehyde has been recommended by the European Environmental Contact Dermatitis Research Group to be 2.0%, that is, the dose of 0.60 mg/cm (wt/vol) instead of 1.0%, which is the concentration previously used for the baseline series in most countries. Without causing any more irritant reactions, the patch test concentration of 2.0% detects twice as many contact allergies and enables the diagnosis of formaldehyde-allergic patients who otherwise would have been missed. The studies that underpin the decision were performed in Europe and partly in the United States. The Finn Chamber patch test system was used. The allergen dose per area was kept uniform with a micropipette. This report describes the background for routinely using formaldehyde 2.0% instead of 1.0% and for using a micropipette when applying the test solution.