Reactions to Quaternium 15, Bronopol and Germall 115 in a standard series

The incidence of positive patch test reactions to Quaternium 15 has increased by a factor of 3 within a relatively stable population over 2 years, while the incidence of reactions to Bronopol and Germall 115 has remained static. The problem of interpreting an apparent positive reaction to a formaldehyde-releasing preservative in a formaldehyde-sensitive patient is discussed.