Loratadine augments emotional blushing

The aim of this study was to determine whether loratadine, a selective inverse agonist of peripheral histamine H₁ receptors, would reduce emotional blushing. Loratadine (10?mg) or placebo was administered orally one hour before 31 healthy participants sang a children's nursery rhyme to evoke embarrassment and blushing. Skin blood flow was monitored via a laser Doppler probe attached to the cheek. Increases in facial blood flow while participants sang were greater in the loratadine than the placebo group (mean increase?±?standard deviation 71?±?52% in the loratadine group versus 35?±?37%, p?=?.036). However, perceptions of blushing were similar in both groups. These findings suggest that loratadine augmented blushing rather than inhibiting it. Thus, histamine released during blushing may inhibit acute increases in facial blood flow by evoking H₁ receptor-mediated vasoconstriction.