Photo Credit: Morsa Images

The following is a summary of “Stability of Diluted Chlorhexidine for Skin Testing in Drug Allergy Evaluations,” published in the November 2024 issue of Allergy and Immunology by Shah et al. 

Chlorhexidine gluconate (CHX) is commonly used for skin testing in allergy evaluations. Its dilution stability, particularly with sterile water for injection (SWFI) or normal saline (NS), remains unexplored. 

Researchers conducted a retrospective study to evaluate the stability and precipitation of CHX when diluted with SWFI or NS for drug allergy skin testing. 

They prepared CHX dilutions (5 mg/mL to 0.002 mg/mL) using SWFI and NS. Stability and precipitation were assessed over 48 hours using high-performance liquid chromatography (HPLC) and UV-Vis spectrophotometry. Turbidity was measured at various time points to monitor precipitation. 

The results showed no significant differences in peak heights between CHX-SWFI and CHX-NS dilutions. Visible precipitation and increased turbidity (>100 NTU) occurred in CHX-NS (5 mg/mL) after 60 minutes. No precipitation was observed in CHX-SWFI at any concentration for 48 hours. 

They concluded that SWFI was the preferred diluent for CHX skin testing above 0.02 mg/mL to prevent precipitation. NS was feasible for dilutions from 0.02 mg/mL to 0.002 mg/mL and reduced injection pain, with reagents stable for up to 24 hours, except for CHX-NS at 5 mg/mL. 

Source: jaci-global.org/article/S2772-8293(24)00168-1/fulltext