BlackLeaf is right see can't touch any royalty and it's not simply protogall either, you see if an ordinary human touches them the ordinary human bursts into flames, sometimes damaging expensive furniture. You Americans have forgotten all this stuff since you left the family.
You cannot touch the monarch. There was a bit of a hoo-hah when Michelle Obama did it in 2009 In fact, she also forgot to curtsey to the Queen, too.
Michelle Obama Touches Queen Elizabeth II on the Back, and does not Curtsy. British forgive her - YouTube
In fact, the Americans seem particularly prone to it, for some reason (maybe they're a more touchy-feely society).
While participating in an official event as part of a Royal Visit to America in 2007, actor Mickey Rooney breached the no-contact rule by grasping the gloved hand of the Queen and enthusiastically kissing it.
During the same Royal Visit, Bush's wife forgot to curtsey to Her Majesty in the White House.
In 1992 Australian Prime Minister Paul Keating earned the name 'The Lizard of Oz' after putting his arm around the Queen during her tour of Australia.