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Bar graph illustrating the number of horses assigned a particular histamine challenge score (HCS). The histamine challenge score (HCS) refers to the dose of histamine when the inhalation was stopped with HCS1 = 32 or 16 mg/mL, HCS2 = 8 mg/mL, HCS3 = 4 mg/mL, HCS4 = 2 mg/mL, and HCS5 = no histamine inhalation possible. *indicates significant difference compared to group C.
