Time-line of the CHS assay showing the order of procedures. Mice were irradiated with a single dose of UVA or consecutive doses of UVA in three days. Three days later from the latest UVA dose, mice were sensitized to the shaved back with oxazolone. Mice were challenged with oxazolone to both ear pinna 7 days after sensitization. The thickness of the ears, i.e. ear swelling, was measured 24 hours after challenge.