'Hypoallergenic cats' go on sale

At just three weeks old these kittens have already been reserved

What are claimed to be the world's first specially bred hypoallergenic cats have gone on sale in the US.

US biotech firm Allerca says it has managed to selectively breed them by reducing a certain type of protein that triggers allergic reactions.

The company says the animals will not cause the red eyes, sneezing and even asthma triggered by cat allergy, except in the most acute cases.

Despite costing $3,950 (£2,104), there is already a waiting list to get one.

Allerca first started taking orders for hypoallergenic cats back in 2004.

No genetic modification

It tested huge numbers of cats trying to find the tiny fraction that do not carry the glycoprotein Fel d1 - contained in an animal's saliva, fur and skin - which often prompts an allergic reaction in humans.

Those cats were then selectively bred to produce the hypoallergenic kittens now on sale, the company says.

The company's Steve May told the BBC that it was a natural, if time consuming, method.

"This is a natural gene divergence within the cat DNA - one out of 50,000 cats will have this natural divergence," he said.

"So candidates - natural divergent cats - were found and then bred so there is really no modification of the gene."

The BBC's Pascale Harter says there could soon be a global market for the kittens - in the US alone 38 million households own a cat, and around the world an estimated 35% of humans suffer from allergies.