Hello kd250787 Welcome to HCM Intravenous drug abuse is very dangerous. It has risk of transmission of many infections like HIV, Hepatitis B, C, it may cause fibrosis in veins, may cause embolic plaques in blood vessels, inflammation and collapse of blood vessels. Taking with unison which is a antihistaminic medication used for sleep just increase dependence to heroin only. The problem is due to repeated injections and it resulted in punctured veins, inflamed veins, collection of hematoma under injection sited or in simple terms thrombophlebitis. Ultimately with time this thing complicates to fibrosis of vein and cord like veins are seen. Its very harmful as if not controlled in time it may lead to blockage of blood supply to affected part may lead to gangrene to part. Systemic infection may occur and this will make you sick. So kindly try to attend rehab programs and quit heroin. What you can do now is- - Apply ice on affected part, this will decrease swelling and will fasten recovery - Thrombophobe cream which is available at local chemists will decrease inflammation and pain at site. - any OTC analgesic medicine for pain - Try not to inject again at affected site. Hope I cleared your doubt. Thanks take care