There's something menacing about mould. Not only is it disfiguring, but it threatens to escalate. "Turn your back," it whispers, "and I will spread. Today I'm a few spots on your cheddar, but tomorrow your whole kitchen will be full of fur. You will only escape by burning the house down."

It's not entirely fanciful, this fear. The microscopic fungi that we call mould can survive cold, dry or acidic conditions that make bacteria curl up their toes and die. They spread their threads through everything from meat and fruit to bread, vegetables, cheese and jam. They're the culinary equivalent of dry rot.

I had a nasty attack recently, while attempting to make bacon. Having made the elementary mistake of trying to dry it in a too-damp cellar, I ended up with five kilos of salted meat that was dusted with white, spotted with blue and marbled with brown. Sticky and rank, it offended the hands and the nose, as well as the eyes.

If you ever find yourself in a similar situation (though you won't, because you're not stupid), all is not necessarily lost. Jasper Aykroyd, who makes his living explaining how to cure meat properly, says that as far as salami or homemade bacon are concerned, although black or brown moulds usually spell disaster, as does anything slimy and white, the powdery white or greeny blue varieties are generally nothing to worry about. They're typically only skin-deep, and if it looks as if they're getting out of hand you can wipe them back into line with a vinegar-soaked cloth.

In fact, he says, the right kind of mould actually enhances charcuterie: "It's an important part of the curing process, particularly with salami. It gives the meat a certain bitterness. In the same way that bitterness adds structure to a beautiful wine, it brings depth to bacon and ham." Which is why many recipes, particularly on the other side of the channel, call for charcuterie to be infected with the powdery white Penicillium camemberti.

The most famous Penicillium, of course, is Penicillium notatum, the mould that gave the world penicillin. But its less glamorous siblings are good friends to the food industry. Penicillium camemberti (again) is sprayed on to camembert and brie to age them and create their white rinds, while Penicillium roqueforti gives blue cheeses such as stilton and roquefort their veins. At Hampshire-based Two Hoots Cheese, creators of three award-winning blues, co-founder Sandy Rose explains that mould is added to the milk at the start of the process, and that the cheeses are pierced twice as they mature, to allow the air to reach the mould beneath the surface. "We once accidentally left the mould out of our Barkham Blue," she recalls. "The ripening process slowed right down, and the flavour was completely different."

Another mould, Botrytis cinerea, is essential to dessert wines such as Sauternes and Trockenbeerenauslese. Grapes attacked by the "noble rot" become partially raisinised, reducing their water content and increasing their sweetness. Many wine-makers will deliberately spray Botrytis spores over their vineyards.

Does this mean we should be more relaxed about mould? Yes and no. Impressively thorough advice from the US Department of Agriculture says you can rescue hard cheese and firm fruit and veg by cutting out at least an inch around and below the mould spot, but advises you to chuck out whiskery hot dogs, cooked meat, casseroles, grain and pasta, soft cheeses, yoghurt, sour cream, jellies, soft fruit and veg, bread, baked goods, peanut butter, legumes, nuts and many more.

Philippa Hudson, senior lecturer in food safety at Bournemouth University, backs up that advice about cheese – though she'd only remove a centimetre or so beyond the surface mould. This will usually be our old friend Penicillium. "But it's important to say that not all of the Penicillium moulds are safe," she adds. "Some of them do produce toxins and you can't necessarily tell which are the bad ones by looking at them. It's not as if all green moulds are good, all white moulds are good and all brown ones are to be avoided." Mind you, she admits, that's not totally useless as a rule of thumb: "You're moving along the right tracks."

How dangerous can moulds be? "Seriously dangerous," she says. "The genus Aspergillus, which grows on peanuts and peanut products, produces a group of toxins called aflatoxins. They can cause liver cancer – and cooking won't destroy them."

That's a message that Peter Wareing endorses. He's the editor of the handbook Common Yeasts and Moulds in Foods, and a food safety expert at Leatherhead Food Research, which carries out independent scientific studies. As well as peanuts, brazil nuts and almonds, all of which can harbour aflatoxins, he warns about apples, where moulds can produce a toxin called patulin.

But there's some good news. According to Wareing, most jam mould can safely be spooned away with no further threat to life and limb, while patulin is destroyed by fermentation. All of which means that so long as you stick to a diet of cider and marmalade, you should be entirely safe.