Multiple sclerosis (MS) is an autoimmune disorder of myelin destruction. Blood-brain-barrier (BBB) disruption precedes pathological or clinical findings and could involve mediators from perivascular brain mast cells, such as histamine and vascular endothelial growth factor (VEGF). Mast cells could be activated by many triggers, including acute stress that has been correlated with MS exacerbations. We considered that the histamine-1 (H₁) receptor antagonist hydroxyzine, which also partially inhibits brain mast cells and has anxiolytic properties, may reduce MS symptoms. This open label, pilot, clinical trial investigated the effect on MS of an oral solution of hydroxyzine (100 mg per day), together with caffeine (200 mg per day) to reduce sedation. Twenty patients (8 males; 12 females) with relapsing-remitting or relapsing-progressive MS completed the study (12 ± 1 months) and were evaluated using disability scales. Most patients on hydroxyzine (75%) remained stable or improved neurologically and all but one showed improved mood. Hydroxyzine could be used as an adjuvant in MS, but the small number of patients enrolled and the short duration of the study precludes any definitive conclusions. A double-blind, placebo-controlled study is warranted.