NSW Food Authority chief executive officer Polly Bennett said the risk of food spoiling and food poisoning is a common concern of many parents, particularly in the warm months of the first school term.

"It is true that as temperatures rise so does the risk of food poisoning," she said.

"So the basic rule of thumb is to keep it cool for school in order to reduce that risk.

"We do see a seasonal trend where the rate of salmonella, one of the most common bacteria associated with food poisoning, increases in summer.

"In the summer months of 2013-14 there was an average of 371 salmonellosis notifications for NSW residents compared to an average of 186 over the winter months."

The best way to keep food safe and also to avoid food spoiling in a lunchbox is to keep it cool.

"The fact of the matter is that there are generally a number of hours between when a school lunch is packed and when it is consumed, but a few simple steps can keep your child's lunch fresh, healthy and safe," Ms Bennett said.

"Food safety is of particular importance for children because they can be susceptible to the more severe consequences of food poisoning."

Ms Bennett said the advice was particularly timely given the Food Safety Information Council had released research showing 25 per cent of parents who packed school lunches did not include a frozen drink or freezer block in their child's lunchbox.

"Putting a frozen drink or freezer block in your child's lunchbox is one of the simplest and most effective ways of keeping the risk of food poisoning at bay," she said.

"The other important thing to remember in going back to school is food allergies, whether it is your own child who suffers or playing your role in protecting other children who may have a food allergy.

"Most NSW schools and childcares have a nut free policy, because it is a high risk allergen, but it is worth checking with your individual school about rules pertaining to foods containing allergens."

Check out the school lunchbox page on the NSW Food Authority's website for plenty of school lunch safety tipswww.foodauthority.nsw.gov.au/consumers/life-events-and-food/kids/tips-for-lunch-boxes