Can I eat parmesan while pregnant?

The verdict

Yes. Parmesan is named by the NHS on its list of cheeses that are safe to eat in pregnancy, and it appears in an unusual place on that list: pasteurised or unpasteurised hard cheeses, such as cheddar, gruyere and parmesan.

That is the only line in the whole of NHS pregnancy food advice where the word unpasteurised appears next to the word safe. Everywhere else, unpasteurised means cook it or avoid it. Hard cheese gets an exemption because of what hard cheese is.

US guidance does not make that exemption. The FDA and ACOG both frame their advice as avoid cheeses made with unpasteurised milk, without a hard-cheese carve-out. That matters in practice for exactly one product: genuine Parmigiano Reggiano, which is always made from raw milk.

Why hard cheese is different

Listeria needs water. Specifically it needs available water, which food scientists measure as water activity, and it needs an environment that is not too salty or too acidic. A ripe brie offers all three: high moisture, moderate salt, and a pH pushed towards neutral by the surface mould.

Parmesan offers none of them. It is pressed hard to expel whey, brined for weeks, and then aged for a minimum of twelve months and often twenty-four or thirty-six. What comes out is a dense, dry, crystalline cheese with a great deal of salt and very little free water. Listeria does not grow in it.

The long ageing is doing double duty. It removes water, and it gives any organism present at the start a very long time in hostile conditions. This is why the NHS is comfortable clearing raw-milk hard cheese while ruling out raw-milk soft cheese, and why the FSA's list of listeria-risky ready-to-eat foods names soft mould-ripened cheeses and raw-milk products rather than hard cheese generally.

Which cheeses count as hard

The NHS names cheddar, gruyere and parmesan, and separately lists pasteurised semi-hard cheeses such as edam as safe. Grana padano, pecorino romano, manchego, comte, emmental and aged gouda are all the same kind of cheese by construction, though the NHS does not name each one.

If you are unsure whether a cheese is hard enough, the test is not the label but the cheese: hard cheese is dry, breaks or crumbles rather than spreads, and does not have a soft, moist paste under the rind. A cheese you can spread with a knife is not a hard cheese.

Parmesan, Parmigiano Reggiano and the US question

The word parmesan covers two different things. Parmigiano Reggiano is a protected Italian cheese made only in a defined area, from raw cow's milk, aged at least twelve months. Cheese sold simply as parmesan, particularly in the US and in supermarket grated tubs, is usually a domestically produced hard cheese made from pasteurised milk.

Under NHS advice, both are fine. The hard-cheese exemption is explicit and covers unpasteurised examples.

Under FDA and ACOG advice as written, a cheese made with unpasteurised milk is on the avoid list, and Parmigiano Reggiano is made with unpasteurised milk. US-sold raw-milk cheese must be aged at least sixty days to be legal, and Parmigiano vastly exceeds that, but the pregnancy guidance is not written around the sixty-day rule and does not mention it.

The practical resolution: if you are in the US and want to follow FDA guidance to the letter, buy parmesan labelled as made from pasteurised milk, which most American parmesan is. If you are in the UK or Ireland, the NHS and the HSE do not restrict it. If you have already eaten Parmigiano Reggiano, this is a difference between two sets of written advice about a very dry aged cheese, not a warning about a food that has caused a problem.

The rind, pre-grated tubs and vending shakers

The rind of a parmesan is edible and is often dropped into soups and stocks. It is the same cheese, dried harder. Simmering it in a soup cooks it thoroughly in any case.

Pre-grated parmesan in a chilled bag is a ready-to-eat food and belongs under the ordinary handling rules: keep it below 5C, follow the storage instruction after opening, and use it by the date. Shelf-stable grated cheese in a shaker is dried further and is not chilled food at all.

The one thing worth a thought is cross-contamination rather than the cheese. A block cut and wrapped at a deli counter has been handled with equipment that may also handle soft cheese and cold meat; a vacuum-packed wedge has not. FSANZ's cheese precaution is to purchase cheeses packaged by the manufacturer.

Salt, and the calcium argument

Parmesan is genuinely useful in pregnancy. It is a concentrated source of calcium and protein, it needs no cooking, and a small quantity delivers a lot of flavour, which makes it a good way to make plain food appetising during a period when a lot of food is not appetising.

It is also very salty. Hard aged cheeses carry more salt per gram than most soft ones, and UK healthy eating advice puts the adult limit at 6g of salt a day. NHS pregnancy diet advice is to include dairy or dairy alternatives while choosing lower-fat and lower-sugar options where possible. The sensible framing for parmesan is as a seasoning: a grating over a dish rather than a portion of cheese in its own right.

If you are worried

There is no action to take after eating parmesan of any kind. Hard cheese is not a listeria vehicle in the way soft cheese is, and no authority describes it as one.

The general safety net applies as always: if you develop fever, chills, muscle aches, headache, a stiff neck, confusion, loss of balance or an upset stomach at any point in pregnancy, contact your midwife or GP rather than waiting it out, and mention anything unusual you have eaten. ACOG notes listeriosis symptoms can appear up to two months after exposure and that treatment with antibiotics is available.

Where guidance differs

On pasteurised parmesan, nowhere. Every authority listed here permits hard cheese made from pasteurised milk.

On unpasteurised parmesan, the UK and the US genuinely diverge. The NHS clears pasteurised or unpasteurised hard cheeses in one sentence. The FDA's pregnancy listeria advice says avoid cheeses made with unpasteurised milk, with no exemption for hardness or ageing, and ACOG says the same. FSANZ lists unpasteurised dairy as higher risk with pasteurised dairy as the alternative, and does not carve out hard cheese either. Ireland's HSE names unpasteurised dairy on its avoid list without qualification.

So the UK is the outlier in permitting raw-milk hard cheese, and it is a deliberate, reasoned outlier rather than an oversight: the exemption is written into the safe list rather than omitted from the avoid list.