"People think 'I will be all right if I slather on sunscreen' but it's not healthy."
Dr Salmon said pale people should not sit in the sun until after 5pm during the summer months.
Further sun safety warnings came from a leading health official, who said people should check their sunscreen was still effective.
Cancer Society manager Fiona Mawley said using expired or heat-damaged sunscreen could be worse than using none, as it could lead to people wilfully exposing themselves to harmful sun while believing they were protected.
"Most sunscreens have a three-year shelf life," she said. "The expiration date gives a fairly definitive timeline for retailers and consumers."
However, sunscreens that expired yesterday did not need to be thrown away.
"If a sunscreen is three months past the expiry date and kept in cool conditions, away from direct and or indirect heat, then it should still be effective to use." Ms Mawley said keeping sunscreen away from heat was the key to preserving its effectiveness.
"The effectiveness of the sunscreen will depend on where it has been stored.
"It is best to store it below 30C - not in a car or golf bag," she said.
"In some cases, the formula could change appearance or split. If that happens, then it should be discarded."
Wearing sunscreen is one of the best ways to help protect exposed skin from sun damage, which can cause skin cancer, including melanoma.
New Zealanders spend just under $3 million on sunscreen at major supermarkets each December, according to data from Nielsen global information and measurement company. However, sales usually slow over January and February, dropping to under $1 million by March.
