Marmalade – In the fridge, especially once opened or if home made.
Marmite – Do not store it in the fridge, because it goes rock hard even if it's a squeezy one. It is so full of salt, it's absolutely fine at ambient.
Pickle / chutney – Read the instructions, some might be safe at ambient temperatures but it depends. As with marmalades and jams, if your friend has made it for you, keep it in the fridge.
Mustard – That does say on the label store in the fridge, but I'm not sure why. It depends on what the manufactures have got in there. For wet mustard read the label and for dry mustard, the shelf is fine.
Peanut butter – At ambient unless it says otherwise.
Salad dressing – Fridge. Apart from the safety reasons for keeping it in the fridge, it can go rancid if kept at room temperature.
Lea and Perrins – Look at the label.
Mayonnaise – Once opened, always in the fridge.
Eggs – They will last longer in the fridge. Once home, put them in the fridge.
Tomatoes – Ambient; they taste nicer. If you want to keep them for a long time put them in the fridge, though.
Bread – Bread in the fridge will go stale faster but it won't go mouldy as quickly. A top tip is to keep your bread in the freezer and pull out slices when you need them.
Butter – Small quantities in a butter dish you can keep at ambient. I wouldn't keep it for any longer then a few days as it will go rancid if you keep it for long periods of time.
As told to Helena Kealey. Dr Lisa Ackerley is from thehygienedoctor.co.uk