No, they shouldn't be, unless he has some sort of disease that causes a depressed immune system, or something like diabetes that causes wounds to heal slower than normal.
JMO. I didn't hang out with heroin users when I was doing drugs, but the people I knew who shot up shot up anythign they could get their hands on, cocaine, they would even melt down crack and shoot it up mixed with lemon juice
Is your BF in rehab? a recovery program of some sort? NA at least?