Four calves from each group of purebred Kedah kelantan (KK), halfbred KK X Friesian, and quarterbred KK X Friesian were experimentally infested with Boophilus micropills larvae. Two calves from each genotype were injected, intramuscularly with antihistamine while the remaining two animals in each genotype received the same dose of antihistamine and dexamethasone. Dexamethasone combined anti-histamine treatment suppress tick resistance as manifested by the production of higher number of engorged female ticks, higher mean weight of replete ticks, mean weight of eggs and mean number of larvae hatched from 1 g of eggs. In anti-histamine treated animals there was no reduction of resistant in all animals as manifested by a few ticks were able to feed successfully. At 1, 2, and 3 hours post-larval attachment in anti-histamine and dexamethasone treated cattle there was complete ablation of the cellular infiltration in the dermis beneath the tick mouthparts, especially eosinophil and basophils. There was little destruction of tissue. However, in anti-histamine treated cattle there were more cellular infiltration and degranulation in the dermis. The cells infiltrating the dermis were mainly eosinophils followed by neutrophs, mast cells and basophils and some of these cells showed sign of degranulation. At 24 hours postlarval attachment, animals lTeated with anti-histamine and dexamethasone showed reduction of, cellular infiltration, degranulation, size of the epidermal lesion and tissue damage. The neutrophils were the predominant cells within the epidermal lesions. However, animals in anti-histamine treatment showed edema, more cellular infiltration and degranulation, and destruction of tissues as compared to antihistamine and dexamethasone treated animals. In anti-histamine treated cattle the epidermal lesions were obviously larger and the percentage of eosinophils and basophils were higher than those of antihistamine and dexamethasone treated animals. KEYWORDS: Kedah-Kelantan cattle, KK X Friesian callie, B. micropflls, dexamethasone, antihistamine, cellular response.