INTRODUCTIONBuprenorphine, a semi-synthetic opiate alkaloid derivative used for treatment of opioid dependence(1). Pruritis has been reported as a side effect with intramuscular and supra-dermal patch of buprenorphine and less common with oral/sublingual use of Buprenorphine.CASE REPORT19 years male presented to OPD of a tertiary care center with history of consuming smack in a chasing pattern for past 9 years, associated with tolerance, withdrawal, inability control the urge, craving and significant socio-occupational dysfunction due to opioid use. He had past history of conduct disorder. Patient was diagnosed with Mental and behavioral disorder due to opioid use, dependent pattern (ICD-10). For opioid substitution he was initiated with tablet buprenorphine sublingual (4 mg), after 1 day later he developed skin reaction- itching and erythema and then vesicular lesion. Consultation liaison with Dermatology department was done for evaluation of the allergic reaction and a drug re-challenge trial to assess for hypersensitivity was done with informed written consent of patient. There was increase in eosinophil counts from a differential count of 5% to 15% after re-administration of sublingual Buprenorphine suggestive of opioid related allergic dermatitis. The symptoms of intermittent itching was reported and managed with Tablet cetirizine 10 mg and local applicant Mometasone and Fusidic acid combination. However, on discontinuation of tablet buprenorphine new lesion didn't erupt whereas old lesion gradually healed. His Buprenorphine was discontinued and symptomatic management was done for withdrawal symptoms.DISCUSSIONThe aetiology of opioid-induced itching is unknown but may be due to either a direct central effect or to histamine release. Reports of allergic contact dermatitis are common with Buprenorphine patch, though uncommon with sublingual Buprenorphine use.CONCLUSIONThe present report describes allergic dermatitis is an uncommon drug reaction with sublingual Buprenorphine use and hence should be dealt vigilantly.