Japanese coronavirus guidelines encourage people to wear masks, but medical agencies warn parents not to wear them on babies because it makes it hard to see changes in facial color, expression and breathing, he said in a leaflet.
Babies have narrower airways and masks can make it harder to breathe, adding strain to their lungs, it continues.
There is also an increased risk of suffocation, especially if a small child vomits behind a mask.
Infants have a relatively low risk for coronavirus infections and the association concludes that masks are not needed for babies under two years.
On Monday Japanese Prime Minister Shinzo Abe raised the country’s national emergency. It has been in place for almost a month but the authorities have appointed it a week earlier than planned.
However, Abe expanded his travel ban to 111 countries in effect Wednesday, now including the United States, India and South Africa.
The list of bans was expanded by 11 countries this week and banned foreign nationals living in these countries from entering Japan.
Japanese citizens are still allowed to enter the country, even though they have to undergo medical tests and quarantine themselves for 14 days.