kina spins just keep going deeper until they hit bone if left under the skin, my mate stood on one, put him out of commission for 3 weeks, they certainly hurt and grabbing them with tweezers is useless they just break up, so best they be dug out.

i have got bits in my hand at the moment that have been in there for about 3 years

I worked as a commercial kina diver for 7 years. Most kina spines cause no problems, and as said before, best to leave them a couple of days - they get slightly infected and then pop out. Better than probing and breaking them into smaller pieces. They don't krrp migrating in general - unlike fish spines that do. 

I drove one in underneath a fingernail, right down to past the cuticle.

I just get a slightly raised lump for a month, but no pain. 

Had lots. Remove them by stabbing them on either side with two hypodermic needles and levering them out.

Dunno that they have much in the way of small molecule chemical toxins  in them, but they swell a bit after a couple of days as above. They come out easy enough with a hypodermic needle once they've swelled a bit. The swelling could be an infection but I always wondered about a direct immune response. There are a lot of proteins involved in biomineralisation that end up incorporated in structures like kina spikes, I'd wager they'd be immunogenic. Have heard of people getting sensitised from things like snapper spikes so might be something in it.

Mate had his arm removed last year after becoming infected with a snapper spike. PM if you need to talk to him

@kaveman, dan v
I don't have any ethics approval yet to contact actual patients but may do soon, thanks

Grasshoppa
So have you also had them in ur hands and get the septic festering and pain like the rest of us?
Can't be fun when they hit the shin bone? (Too much weight belt perhaps..?!)