Contact allergy to formaldehyde. Diagnosis and clinical relevance

Sammanfattning: Preservatives are biologically active substances mainly used in water-based products to prevent the growth of microorganisms. Most people are exposed to them on a daily basis. Formaldehyde is one of the oldest and most commonly used preservatives. However, it is a well-known contact sensitiser in dermatitis patients. The aims of this work were: i) to investigate the prevalence of contact allergy to formaldehyde using the baseline patch test series; ii) to determine the optimal patch test concentration and dose for formaldehyde; iii) to study the clinical relevance of contact allergy to formaldehyde detected by formaldehyde 2.0% (0.60 mg/cm2) but not by formaldehyde 1.0% (0.30 mg/cm2); iv) to study the effects of low concentrations of formaldehyde on irritant contact dermatitis in formaldehyde-allergic patients; v) to semi-quantify the formaldehyde content in skin care products used by patients with suspected allergic contact dermatitis, and compare this with the declaration of contents; vi) to determine whether formaldehyde-allergic patients are more exposed to formaldehyde in skin care products than dermatitis patients without contact allergy to formaldehyde; vii) to investigate the patterns of concomitant contact allergy to formaldehyde and formaldehyde releasers. The findings were as follows: i) patch testing with 15 μl formaldehyde 2.0% (0.60 mg/cm2) using a micropipette detects significantly more reacting individuals than 1.0% (0.30 mg/cm2), without a high frequency of irritant reactions. ii) individuals who react to formaldehyde 2.0% (0.60 mg/cm2) but not to 1.0% (0.30 mg/cm2) have a significant risk of developing an eczematous reaction when exposed to concentrations of formaldehyde allowed by the EU Cosmetic Directive. iii) daily exposure to low concentrations of formaldehyde is sufficient to exacerbate existing dermatitis in patients with contact allergy to formaldehyde. iv) to assess exposure and clinical relevance in formaldehyde-allergic patients, the patients’ skin care products should be analysed, especially when the labelling of the products does not include formaldehyde or formaldehyde-releasing preservatives.