Can I eat mayonnaise while pregnant?

The verdict

Shop-bought mayonnaise is safe in pregnancy in every country covered here, and it is worth stating that plainly because a great many people avoid it unnecessarily.

The FDA is explicit: commercial mayonnaise, dressing and sauces contain pasteurised eggs that are safe to eat. FSANZ lists commercial custard and dressings, giving mayonnaise and aioli as its examples, among the safer alternatives to raw and lightly cooked eggs. Neither the NHS nor the HSE restricts shop-bought mayonnaise.

The restriction is aimed at mayonnaise made fresh from raw eggs, which is a different product. The FDA lists homemade mayonnaise among foods to avoid because they may contain raw or lightly cooked eggs, alongside Caesar salad dressing, bearnaise sauce, hollandaise sauce, aioli sauce, homemade ice cream, mousse, meringue and tiramisu. Ireland's HSE names foods made with raw or under-cooked eggs, such as homemade mayonnaise, on its avoid list. FSANZ names mayonnaise and aioli among raw and lightly cooked egg foods in its higher-risk table.

The UK is the exception, and the reason is a national egg scheme.

The British Lion exception

The NHS states that foods like mayonnaise and mousse made with raw eggs are safe in pregnancy if they are made with British Lion eggs or hen eggs produced under the Laid in Britain scheme.

Those schemes involve vaccination of laying flocks against salmonella together with flock monitoring and traceability, and the NHS's reasoning is stated directly: British Lion hen eggs and hen eggs produced under the Laid in Britain scheme are less likely to contain salmonella. The NHS also puts the risk in proportion, noting that salmonella is unlikely to harm your unborn baby, but you could get food poisoning, which can make you seriously unwell.

Eggs without that assurance should only be eaten well cooked, and the NHS says hen eggs that do not have the stamp should not be eaten raw or partially cooked. Duck, goose and quail eggs must be well cooked in all cases.

No other country covered here has an equivalent scheme, which is why no other country offers the exception. The FDA's route to the same place is pasteurised eggs: it lists fresh pasteurised eggs in the shell, liquid pasteurised egg products, frozen pasteurised egg products and powdered egg whites as ways to make raw-egg recipes safely.

How to check

British Lion eggs carry a red lion stamp on the shell and on the box; Laid in Britain eggs carry that scheme's logo on the packaging. If you are making mayonnaise at home in the UK, look for one of those.

If you are eating mayonnaise or aioli made in a restaurant kitchen, you cannot check, and the honest answer is to ask. Many kitchens use pasteurised liquid egg for exactly this reason. If nobody can tell you, treat it as unassured.

Where mayonnaise actually turns up

The jar is easy. The complications are in dishes where mayonnaise is an ingredient.

Coleslaw, potato salad and prepared sandwich fillings from supermarkets are made with commercial mayonnaise and are not restricted for the mayonnaise. They are chilled ready-to-eat foods, so the usual handling rules apply: the NHS groups pre-packaged salads among foods to be careful with, to be kept chilled and eaten before the use-by date.

An egg mayonnaise sandwich raises two separate points and neither is the mayonnaise. The eggs in it are hard-boiled and therefore well cooked. The sandwich itself is a chilled ready-to-eat food, which is why the NHS lists pre-packaged sandwiches containing eggs among foods to be careful with.

Caesar dressing is the one worth naming, because the traditional recipe uses raw egg yolk and it is often made fresh in restaurants. The FDA lists Caesar salad dressing among foods to avoid for that reason. Bottled Caesar dressing is made with pasteurised egg.

Deli counter and salad bar mayonnaise-dressed salads are a handling question rather than an egg question, and the HSE advises avoiding deli counters as food hygiene may be compromised. FSANZ lists pre-prepared salads, including those from buffets and salad bars, in its higher-risk table.

Vegan mayonnaise and other alternatives

Vegan mayonnaise contains no egg, so the salmonella question does not arise at all. It is still a chilled or ambient ready-to-eat product and should be kept and used as the label says.

Yoghurt-based dressings made with pasteurised yoghurt are unrestricted. Home-made mayonnaise using pasteurised liquid egg is a straightforward substitute if you want to make it yourself and cannot get assured eggs.

Heating is not a practical option for mayonnaise, since it splits, which is why the answer here rests on the egg rather than on cooking.

Leaving mayonnaise out

The old warning about mayonnaise spoiling at picnics is largely backwards. Commercial mayonnaise is acidic, which suppresses bacterial growth; the risk in a picnic potato salad usually comes from the potato, the chicken or the egg rather than the dressing.

That said, the general rules still apply. The FSA advises keeping chilled food below 5C and eating ready-to-eat food within four hours of leaving the fridge, or two hours on a very warm day. FSANZ describes the danger zone as 5C to 60C and advises limiting time spent in it.

A mayonnaise-dressed salad that has sat in the sun for an afternoon is not a good idea in pregnancy, and the mayonnaise is the least of the reasons.

If you have eaten homemade mayonnaise

The realistic outcome is nothing at all. Salmonella in eggs is uncommon, and the NHS notes that salmonella is unlikely to harm your unborn baby, though it can make you seriously unwell.

Watch for food poisoning symptoms over the next day or two: nausea, vomiting, diarrhoea, stomach cramps and fever. NHS advice is to get help from 111 if you feel unwell after having food that should be avoided in pregnancy, or if you have had vomiting and diarrhoea for more than 48 hours. Dehydration is the main practical risk, and ACOG notes that vomiting and diarrhoea can cause the body to lose too much water, which can be dangerous for you and your fetus.

If you are simply worried rather than unwell, there is nothing to test for and nothing to do.

Where guidance genuinely differs

Everyone agrees that commercial mayonnaise is safe and that raw egg is the concern.

The UK is alone in allowing raw egg foods outright, and it can do so because it has a national assurance scheme to point at. The NHS names mayonnaise and mousse specifically as foods that are safe when made with British Lion or Laid in Britain eggs.

The US, Australia, New Zealand and Ireland have no equivalent scheme, so their advice defaults to avoiding raw egg foods or using pasteurised egg. The FDA offers pasteurised shell eggs and liquid egg as the workaround; FSANZ lists pasteurised eggs and commercial dressings as its safer alternatives.

If you are in the UK, check for the lion. If you are anywhere else, use the jar.