Why do some women develop allergies when pregnant?

No two pregnancies are the same. As new life begins to grow, the hormones behind it can leave some women with a lot more than they bargained for.

Despite never having an issue with a certain food before, it can be quite normal for expectant mums to develop intolerances and even allergies to certain foods.

It is also just as possible for women with known food allergies to bid farewell to them throughout their pregnancies.

Sydney nutritionist and cofounder of The Health ClinicPip Reed specialises in women’s health and tells Babyology this allergy phenomenon is quite common.

“It can go either way though, some women experience more allergies and others find their allergies are actually suppressed when they’re pregnant,” Pip says.

She says it is the case for both environmental and food allergies.

“About a third of women will experience that increase in nasal swelling and runny nose and itchiness when they are pregnant – that’s more to do with hormones,” Pip says.

“With food allergies, there are the most common ones, being to milk, eggs, wheat, soy, peanuts, tree nuts, shellfish, that women may be more prone to experiencing during pregnancy.”

Suppressed immunity

Cropped image of a pregnant woman with a bowl of strawberries

Pip says intolerances or allergies to more random foods such as almonds or strawberries, could mark the temporary return of childhood reactions as our immunities become suppressed during pregnancy.

“They may have had a slight intolerance when they were a child and they’ve outgrown it and, therefore, because our immune systems become suppressed when we are pregnant it returns,” Pip says.

“I know it sounds like a mean thing to say but you’ve got to think the baby is a parasite in itself, so our bodies naturally have got to suppress our immune systems to stop our bodies from attacking the baby.

“Because of that some women do experience allergies. They go from being able to eat almonds all their life and suddenly they have an allergy while they are pregnant and even while breastfeeding.”

Intolerance vs allergy

There is a big difference between having a food intolerance and having a food allergy, Pip says.

“An allergy is when your body develops antibodies that attack that particular food and think it is a foreign and bad thing for the body,” she says.

“Intolerance – for example, lactose intolerance – is more to do with the fact you don’t have enough lactate in your stomach to break down the lactose so people with an intolerance will be able to have a certain amount of certain foods before they feel a reaction. Most people, I find, will have a cup of milk and then feel sick.

“With allergies, generally you can eat the food the first time and then when you have it the second or third time, the reaction develops and just gets worse and worse. Anything that goes anaphylactic is very dangerous for both you and baby.”

Don’t take risks

Pip says even if pregnant women do get a break from the allergies that once plagued them, it is important to remain cautious.

“Some doctors say we should experience less allergies when we are pregnant because our immune system is suppressed so things we were allergic to we should now possibly not have an intolerance to, but it’s best to be considered on a case by case basis,” she says.

“If you have a severe allergy, especially anaphylaxis, before you are pregnant, you wouldn’t go near it during pregnancy and you would carry an Epi-pen.

“Anaphylaxis is more to do with the blood, the body shuts down and the blood stops flowing and, if you’re not looked after, it can kill the baby and yourself. It is highly dangerous.”

Signs and symptoms


Pip tells Babyology women should seek professional help from a doctor or registered nutritionist if they start noticing any sign they may be having an adverse reaction to food.

“Symptoms include having an itchy and runny nose, an itchy throat or feeling a tingling sensation in the tongue, lips or throat,” she says.

“Look out for skin reactions such as a break out of eczema, rash and hives.

“More serious symptoms might include cramping, diarrhoea and vomiting.”

Probiotic benefits

One of the first things Pip says she recommends to her clients, especially those with a history of eczema or asthma, is to take a good probiotic throughout pregnancy for mum’s health and to reduce the chance of passing it on to baby.

“Research say probiotics through pregnancy and after birth for a couple of years reduces the instances of asthma and eczema by around 7 per cent plus,” Pip says.

Take note

  • Pip says pregnancy cravings can be a sign of an allergy or intolerance.
  • Seeing a nutritionist for advice before and during pregnancy is a good way to ensure you’re not missing out on important nutrients.
  • The same hormones there to protect the baby during pregnancy can compromise the immune system.
  • If you do have an intolerance or allergy, Pip says in some cases it’s best if mum refrains from having that food until after breastfeeding to avoid passing the allergy or intolerance on to the baby.


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