Salivary tick protein that acts by scavenging histamine at the wound site, outcompeting histamine receptors for histamine, thereby overcoming host inflammatory responses (PubMed:10360182). Binds histamine with a high-affinity (Kd=1.2 nM) (PubMed:10360182). Contains two binding histamine sites (H and L), that appear to bind histamine with differing affinities (By similarity). Homodimer; disulcde-linked. Expressed by salivary glands. Exclusively secreted by larvae, nymphs and adult male ticks. Contains 2 sites/pockets that bind histamine with different affinities. Site H (high affinity) is indicated here as binding to histamine 1, and site L (low affinity) is indicated as binding to histamine 2. N-glycosylated. Belongs to the calycin superfamily. Histamine-binding salivary protein family.