no
The seeds are poisonous if ingested.
Only to animals.
I would not use powder. Any flea shampoo is fine, also you could use a flea collar.
Yes they are poisonous if ingested
Metal poisoning is a toxic accumulation of metals in the body. Some metal elements that are poisonous if ingested are mercury, lead, aluminum, arsenic and cadmium.
No sulfur powder is a non toxic formula almost like baby powder it will not harm humans or cats if ingested but will give you a very nasty taste.
flea powder
It can yes.
Several are such as lead, but mercury (the only metal that is a liquid at room temperature) is very poisonous.
Probably, depending on the dose ingested. I would certainly call an animal emergency hospital and ask their advice.
Not naturally, but they do contain bacteria that cause serious sickness if ingested.