After 9 months of avoiding soft cheese, pate and hard boiling your eggs, suddenly you’re free to eat whatever you like again without worrying about the impact on your unborn baby.  However, don’t go diving headfirst into the prosecco just yet!  If you’re a breastfeeding mum, you need to be aware of your diet because traces of all the foods you eat will end up in your breastmilk. Usually this is a good thing: some experts believe that breastfed babies enjoy the variation in flavour caused by day-to-day changes in your diet. The downside is that certain foods can irritate your baby’s digestive system or, more rarely, trigger allergies.

The differences between irritants and allergens

It’s important to distinguish between foods that can irritate your baby and those that can trigger full-blown allergies, known as food allergens. As far as irritants go, some breastfeeding mums find that ‘windy’ vegetables like cauliflower, cabbage and onions upset their babies, while others swear that hot, spicy foods leave their babies unsettled after feeds. Other possible irritants include chocolate (which can cause diarrhoea), nicotine, alcohol and caffeine.

Meanwhile, the foods that most commonly trigger allergies in babies are peanuts, cow’s milk, tree nuts (such as almonds and walnuts), fish, shellfish, sesame seeds, egg, wheat and soya. Although allergies are quite rare in babies – only about 3-4 per cent are affected – it is possible for exclusively breastfed babies to have allergic reactions to foods in their mothers’ diets.

Will it happen to my baby?

When your baby is born, there’s no way of knowing whether he’ll be sensitive to irritants in your diet. However, we do know that babies who have a strong family history of allergies are more prone to allergies themselves. ‘Infants who have a history of allergies on both sides of the family have a 60-80 per cent risk of developing an allergy or allergic condition, such as asthma, while those with allergies on one side have a 30-50 per cent chance,’ says Carina Venter, an allergy dietician at the Hide Asthma and Allergy Research Centre in the Isle of Wight.

Food allergies are the most common kind of allergy in babies and the main triggers are cow’s milk and eggs. ‘Up to two and half per cent of children under three are allergic to dairy products, while up to one and a half per cent are allergic to eggs,’ says Carina.

Irritants – the signs and symptoms

If your baby is irritated by something in your diet, he may become unsettled, windy or cry inconsolably after a feed. He may also sleep badly. Symptoms will improve within 24 hours.

Common irritants

Cauliflower, broccoli, cabbage, Brussels sprouts, peppers, onions, garlic, spicy foods, chocolate, caffeine, alcohol, nicotine.

What to do

Keep a diary of the foods you eat and your baby’s behaviour for a couple of weeks to see if you can trace unsettled periods back to a certain food or foods. If you do pinpoint the culprit, do talk to your health visitor before cutting that food out of your diet.

Allergies – the signs and symptoms

‘Allergies can vary significantly in severity – from a mild bout of diarrhoea a few hours after a feed to immediate breathing difficulties and even anaphylactic shock (a severe allergic reaction), although this is very rare in breastfed babies,’ says Carina. Other possible allergy symptoms include: hives (a blotchy, raised rash), itching, rashes or redness of the skin, breathing difficulties, facial swelling, vomiting, eczema and blood in stools.

Common triggers

Cow’s milk and eggs are the most common causes of allergies in babies, but peanuts, tree nuts (such as almonds), fish, shellfish, sesame seeds, wheat and soya are also common culprits.

What to do

If you suspect your baby is allergic to something you are eating, it’s important not to alter your diet suddenly. There’s no need to give up breastfeeding, either.

Instead, you should see your GP, who will rule out any other conditions that may be causing your baby’s symptoms. She may then refer your baby to a paediatrician, allergist or dietician for further investigations and tests. You may be asked to keep a food diary and possibly eliminate certain foods from your diet for a while as well.

If your baby is found to have an allergy to a certain food or foods, your doctor or dietician will recommend that you remove these foods from your diet completely. They’ll also give you advice on how to adjust your diet so that it’s still balanced and nutritious for both you and your baby.

If your baby has a severe reaction following a breastfeed – if he develops breathing difficulties, swelling in his face or starts to turn blue, for example – phone an ambulance straightaway.

Should I avoid peanuts while I’m breastfeeding?

There’s no clear evidence that eating peanuts while breastfeeding affects your baby’s chances of developing a peanut allergy. If you have any questions or concerns, you can talk to your GP, midwife or health visitor.