Combination treatment for allergic conjunctivitis - Plant derived histidine decarboxylase inhibitor and H1 antihistaminic drug.

Aim of present investigation was to study the effect of catechin and the combination of catechin and cetirizine in ovalbumin induced animal model of allergic conjunctivitis. Guinea pigs were divided into 5 groups: normal control, disease control, disease treated with catechin 100 mg/kg, disease treated with cetirizine 10 mg/kg, disease treated with combination of catechin and cetirizine, 50 mg/kg & 5 mg/kg respectively. Sensitization was carried out by intraperitoneal injection of ovalbumin for the period of 14 day. Simultaneously, catechin was administered orally for 14 days while, cetirizine was administered at the day of experiment. Determination of clinical scoring, mast cell and blood histamine content, histidine decarboxylase activity from stomach was carried out. Vascular permeability was measured by dye leakage after secondary challenge of allergen and conjunctival tissues were subjected for histopathological examinations. Treatment with catechin, cetirizine and combination showed significant (P < 0.05) decrease in clinical scoring and vascular permeability. While, catechin 100 mg/kg and catechin 50 mg/kg showed significant (P < 0.05) decrease in histamine content in mast and blood. The treatment also showed significant (P < 0.05) decrease in the histidine decarboxylase enzyme activity. However, cetirizine group did not show any difference in enzyme activity as well as histamine content. Histopathological examination also showed improvement in ulceration and decrease in edema and inflammation in all treatment groups. From the present study, we can conclude that catechin exhibits potent anti-allergic activity by histidine decarboxylase enzyme inhibition and combination shown significant anti-allergic activity at reduced dose by both enzyme inhibition as well as inhibition of histamine receptors.