Doctors say one of the biggest risks now is secondary infection
The first planeload of medicines donated by UK drug companies has landed in Haiti, with emergency kits to treat as many as 20,000 people.
UK drug companies have pledged £5.6m in donations, with more flights planned carrying antibiotics, pain killers and anti-fungals, among other supplies.
These have been specifically requested by Haitian authorities, organisers say.
The aid arrived as the Disasters Emergency Committee said its Haiti appeal had now raised £38m in the UK.
The flight took off from Newquay in Cornwall on Wednesday and landed in Haiti on Thursday afternoon.
Anthony Dunnett is president of International Health Partners (IHP) - the organisation that co-ordinates offers of medical aid to disaster zones and works closely with local and international aid bodies.
He said: "We have to ensure that the medicines we send to Haiti are exactly what are needed by doctors on the spot so that patients gain maximum benefit.
The Disasters Emergency Committee is co-ordinating an appeal to help the people of Haiti
There are 13 charities involved including the British Red Cross, Islamic Relief and World Vision
Donate via the
or by calling 0370 60 60 900
"Arrangements are in place to ensure that these supplies reach patients with the minimum of delay once the aircraft has landed."
Among the UK charities operating in Haiti is Save the Children, which is working to set up a supervised children's play area at one of the makeshift camps in Port-au-Prince now home to thousands of earthquake survivors.
Among the children at the camp - in the grounds of a church - is eight-year-old Angelo Sideron Maillard, whose mother and seven siblings all survived but who lost their home and all their possessions.
Describing the moment the earthquake hit, he said: "I was looking for my mum and I was really scared.
"Now we don't even have a tent to sleep in. I don't have anything, not even clothes."
He added: "I would like to go back home but I know that it's impossible now. I'm not going to school any more. It's a shame because I like school."
Other supplies being flown in from the UK include toilet and water treatment kits sent from the Red Cross base at Warmley, South Gloucestershire, on Wednesday.
A Red Cross spokesman said it was also including advice leaflets on how to minimise risks while cooking and other basic hygiene measures.
Diggers are also being sent to construct latrines.
Seven hundred ShelterBoxes are on their way from the UK to Port-au-Prince.
The supplies include 40 tonnes of aid, with enough shelter for 7,000 people.
Authorities in Haiti have announced plans to house 400,000 earthquake survivors in tented villages outside the capital, Port-au-Prince.
An estimated 1.5 million people were left homeless by the 7.0-magnitude quake, which killed as many as 200,000.
At least 75,000 bodies have so far been buried in mass graves, the government has said. Many more remain uncollected in the streets.