dark chocolates

People can be very sensitive or allergic to anything.

Eating large amounts of chocolate can sometimes make pre-existing health issues worse and often triggers more severe symptoms in those with a history of migraines or gastro problems.
Anything that contains ingredients like caffeine, nicotine, beta phenylethylamine or is high in saturated fat can lead to food intolerance symptoms being experienced very quickly by people that are sensitive to them.

I received a lovely box of dark handmade luxury chocolates. do dark chocolates with high cocoa content. I have a headache since eating them. Is it possible these could be the cause?

Can you be intolerant to this?

Does the dark chocolate contain milk or cream? if so, you may have a lactose intolerance.

Could be, but id say unlikely as most dark chocolate does not contain any milk.