What are the rules on travelling with breast milk?

A mother has complained she was forced by security at Heathrow Airport to throw away nearly 15 litres of breast milk. But what are the rules on carrying milk, asks Claire Bates.

Jessica Coakley Martinez, from California, posted an open letter on Facebook, and said she had been travelling without her children on a two-week business trip. She had expressed the milk to feed her youngest son on her return home.

She said she had carried the milk, which was in both liquid and frozen form, as hand luggage through four different countries by air. "You made me dump out nearly two weeks worth of food for my son," she said.

Liquids have been restricted on flights in much of the world since a plot to bomb airliners in 2006. They can go in the hold but those in hand baggage must be in 100ml containers and add up to less than a litre.

There has been an exception for breast milk in the EU since 2006.

A parent can take breast milk on a plane as long as they are travelling with a baby or infant, the UK's Department of Transport says. It must only be enough to feed the child during that journey. More than that must go in the hold.

However, Coakley Martinez said the rules were unfair to "working mothers like me who... spend time away from their baby, but intend to continue to breastfeed them".

In the US, breast milk was allowed in 2007. In 2013, the Transport Security Authority (TSA) said parents flying without their children from the US could carry breast milk in hand luggage as long as it was declared to security. No maximum quantity was given.

Most of Coakley Martinez's milk was frozen but that still counts as liquid. She said she offered to check the milk into the hold. "But that wouldn't work either according to you because I had crossed the border and the only way for me to check the bag now was to exit the airport and re-enter - which I was also willing to do. But you wouldn't give me the milk back - because now it was a 'non-compliant item' and needed to be confiscated."

A spokesman for Heathrow Airport says: "We do appreciate that this has been a frustrating experience. Passengers travelling with their babies are allowed to bring through a reasonable amount of breast milk and baby food outside of their normal 100ml liquid allowance. When travelling without your child, the restriction limits apply without exception."

Subscribe to the BBC News Magazine's email newsletter to get articles sent to your inbox.