Occlusive patch tests were used on 46 chromium-hypersensitive patients to determine the threshold of sensitivity for chromium in distilled water, in alkaline buffer solution (pH 12), and in petrolatum. Chromium in alkaline solution was the most sensitive test method (mean threshold 0.08%), then came chromium in petrolatum (0.15%), and, finally, chromium in distilled water (0.27%).
Percutaneous absorption studies on guinea pigs showed increased absorption of chromium from alkaline solutions compared with the two other vehicles. We consider that this condition is probably the cause of the greater sensitivity when patch testing with chromium in alkaline solution.
Skog E, Wahlberg JE. Patch Testing With Potassium Dichromate in Different Vehicles. Arch Dermatol. 1969;99(6):697-700. doi:10.1001/archderm.1969.01610240055009