The Red Cross in Vanuatu says volcano evacuees urgently need more tents, spare clothes, blankets and washing kits.
Most of Ambae's 11,000 people are now in 74 evacuation centres on the neighbouring island of Santo after fleeing the erupting Monaro volcano.
The charity's organiser on Santo Shirley Johnson said some of the centres were housing double the number of people they should be and 1500 more tents are needed.
She said there was an urgent need for other basic items.
"They need clean clothes, they need soap to keep them healthy. These people, some of them, they just move out here, they don't have, they don't bring anything, they just come up with like three clothes and that's it."
Shirley Johnson said, on the whole, the evacuees were coping well despite being away from their homes.
The alert level for Monaro has been reduced from the second highest setting to level three, but the state of emergency remains in place.