Some parents are struggling to get enough milk formula to feed their babies due to unprecedented demand for New Zealand formula.
Overseas demand has been high since the 2008 San Lu scandal in China, where babies died from melamine-contaminated formula, and the industry says a shortage of goats milk is making things worse.
Progressive Enterprises, which represents Countdown and Foodtown supermarkets says some parents are panic-buying and stockpiling when stock arrives.
Merchandise manager Andrew Dixon says much of the shortage is due to thousands of people sending cans to friends and family in China.
"That's where a large proportion of the demand is coming from, it's not a malicious or covert secondary tier market," he said, though he added that such a market does exist.
Foodstuffs, which represents New World and Pak'n Save supermarkets, has also seen an increase in customers wishing to buy baby formula, apparently to send overseas.
Nutricia's Karicare brand supplies about 80% of the country's baby formula.
Medical sales manager Talei Presland says demand for goats milk formula in particular has grown three-fold in recent years, and when it runs out there is pressure on the rest of the range.
The company has had a big increase in calls from distressed parents in the past couple of weeks.
The Dairy Goat Co-operative, which supplies powder to Karicare, is trying to recruit more goat farmers but says there is no short-term solution.