Paul Salmon, of the Skin Centre, said even the cheapest sunscreens offer good protection. It came down to how much sunscreen people used, rather than which product. Most people don't use enough sunscreen.
It's generally only worth buying a more expensive sunscreen if you won't be able to apply it regularly. Some pricier versions can last up to eight hours but most cheaper varieties only last a couple of hours.
New Zealanders spend $14 million each year on sunscreen.
Antibacterial handwashes
Supermarket price: up to $5
If you hope using a handwash labelled "antibacterial" will keep you healthier, you may be disappointed.
Consumer, in agreement with the US Food and Drug Administration, says research shows that they are no better than products without antibacterial chemicals.
Vitamin C supplements
Supermarket price: up to $31
Professor Margreet Vissers, from Otago University, says most people do not need to take these. In a study, she found eating vitamin C from kiwifruit was vastly superior to
taking it in tablet form. "If you eat well you'll get more than enough for your daily needs."
When people are sick, their bodies need more than they get easily from food and, in those circumstances, a supplement would be worthwhile. But taking a lot is no better. "You make expensive urine that way."
Whitening toothpaste
Supermarket price: up to $10
Whitening toothpaste can cost three times as much as the standard variety but will not make a huge difference. The whitening ingredient in it is much milder than a dentist would use, so you won't get striking results. Consumer says they should reduce surface staining but won't lighten the natural colour of your teeth.
Simply brushing your teeth for longer with an ordinary toothpaste is likely to achieve the same effect.
Photo / Thinkstock
Cough syrups
Supermarket price: up to $14.50
When their child has a cold, many parents reach for a bottle of cough medicine. But a 2007 study showed no good evidence for or against the medication for coughs.
It found syrups did seem to provide relief but that could be from the sugars that coat the throat and ease irritation. Best Practice Journal New Zealand said the placebo effect may also be at work, and honey could be used as an alternative.
Vissers says for adults, sucking a lozenge is likely to be as good as cough medicine. "In extreme cases, a cough syrup is a helpful thing but it depends on what's triggering the cough. For most people something that smooths the airways and creates saliva so it doesn't dry out is enough."
Kiwis spend more than $50 million a year on cough and cold products.
Bottled water
Supermarket price: up to $7.99 for 5 litres
If 30 years ago you said Kiwis would eventually spend more than $60 million a year buying tapwater you might have been called mad.
Experts say there is usually no need to buy bottled water in New Zealand. A Massey University study found microbiological contamination in bottled water, and University of Canterbury toxicology professor Ian Shaw said there were also concerns the chemicals that leaked into the water from the plastic could be damaging.
A 2002 study of 122 countries found our tap water was the third-best in the world.
"In London, it's almost a necessity because the water tastes foul.
In Christchurch, what comes out of the tap is bottled water," Vissers said.
