From Blanco et al. doi.org/10.1016/j.heliy… "The most commonly prescribed antihistamine was cetirizine (46.6%), due its safety profile." "The second and third antihistamines most commonly prescribed were dexchlorpheniramine (35.7%) and ebastine (1.7%)."

For mode of action, I refer you to Malone et al. doi.org/10.3389/fphar.2… - we proposed that dysregulation of mast cells is important in COVID-19.

Aspirin is also a mast-cell stabilizer plus a cox-1 (stronger) and cox-2 inhibitor - see also: dx.doi.org/10.2139/ssrn… for blocking cox-2 with celecoxib combined with high dose famotidine. Clinical evidence supporting aspirin include: doi.org/10.1371/journal…, doi.org/10.1097/ALN.000…, and 10.1213/ANE.0000000000005292