While ketotifen blocks histamine H1 receptors and the release of inflammatory mediators, and is used to treat asthma, rhinitis, skin allergies, and anaphylaxis (36, 50), dextromethorphan is primarily a σ1-receptor agonist and used as an alternative to opioid-containing cough suppressants (51, 52). Here, HRH1 is linked to anaphylaxis.