K. First, You would KNOW if you were contagious. You must trust your instinct....but from your obvious concern, I'd venture to say yes.
(Are you using head and shoulders?)
Here are just my latest interpretations on what the sensations mean:
Biting/Stinging/Tingling/Itching: BAD. Means they are infesting. Scary time. Immed. Decontaminate in shower with borax. Figure out what you did to get bit (pick up a dead bird? dog dish? fish tank? laundry?)
Crawling: Not terrible, esp if no biting follows. Crawling means they're not happy with what you just did, so they're trying to move away surreptitiously, to avoid another treatment of same. Rubbing alcohol ends crawling- apply with tissue or cotton ball to exact spot of crawling...do NOT put pressure. Dispose of alcohol-saturated tissue properly. (haz mat). You're probably not contagious unless you feel like you are shedding.
Dripping/Raining/Popping off your body at a rate of, say, 1-2 per minute: They are abandoning ship. If you have enough salt in your system, I think they'll do this in response to internal B complex, or oregano oil, or a NOVEL substance of similar nature. I'd say you're mildly contagious when this is going on. (They are encased in salt when they drip off, so they're kinda stuck til they find some moisture...so no hugs.)
Shedding: You are doing a half-assed job eradicating them, so they come and go as they please, and you're pretty darn contagious to anyone susceptible since shed morg are in their natural dispersal form, and they are floating like little ashes, dust particles or insects. This is when electromagnetic attraction comes into play re: susceptibility...they can "fly"
Non-treating: (starts appx 24 hours after last treatment [of any sort]) You are tolerating your parasite load, taking a break from treatment; they will be very quiet, because they don't want you to start treating again. You are Very un -contagious but also in a dangerous spot because you think they're all gone, so you might stop treatment, which = v. bad. Don't take a break for more than 24 hours.