Inside: A beginner’s guide to CMPA in babies
If you have found this post then you are most likely Googling in a blind panic, wondering whether your child has a milk allergy or wondering what on earth to do if you have indeed had a doctor confirm your worries.
Please know that I have been there and the entire reason I set my blog up in the first place was to help other mothers in this situation.
I found myself so incredibly lost back in 2013 when my baby was struggling to feed and absolutely nobody would listen.
I will listen to you (you can message me any time over on Instagram) and I will hopefully give you the information you seek, as well as giving you support and courage to get through this.
And you will, you know, you will and it will all be ok. I promise.

What is CMPA?
A cow’s milk protein allergy (also known as Cow’s Milk Protein Allergy or CMPA) is where your body has an abnormal response to the proteins present in the milk – seeing them as a threat.
This can cause the immune system to be ‘sensitised’ to the proteins, causing allergic reactions each time the body comes into contact with them in the future.
Symptoms of a milk protein allergy
It is likely that your baby is showing signs and that is what has brought you here. Well-meaning friends and family will tell you that all babies cry and that they don’t sleep for at least the first 3 months.
And while this is, of course, correct, there is a difference between crying because they are hungry and crying because they are in constant pain.
And a difference between a baby that wakes frequently in the night for feeds and a baby that literally never sleeps.
The main symptoms are:
- Excessive crying
- Poor sleep (constantly awake and uncomfortable)
- Vomiting
- Diarrhoea (slimy/ green nappies)
- Blood in poo
- Constipation
- Eczema
- Hives
- Poor weight gain
- Congestion
- Conjunctivitis
- Anaphylaxis
My experience of a milk allergy in my children came in the form of excessive crying, a complete inability to fall asleep (they never napped – ever!), explosive mucousy poos, hives and congestion.
Each baby is different and so please don’t feel like you need to have ticked off all of these symptoms to ‘qualify’ your worries.
How to confirm a CMPA allergy
There are two types of allergy to be considered here, an an IgE mediated (typically an instant reaction) vs a non-IgE mediated (delayed) reaction.
The more severe the allergy, the quicker you will notice the symptoms appearing. Anaphylaxis would be one example of an instant reaction and of course, if this happens you must immediately call for an ambulance.
In the case of an instant reaction, it is easy to diagnose because it is quite clear what caused the issue. The problem with CMPA is that many times the reaction is delayed ( gastrointestinal symptoms being an example ).
And therefore you can’t be waiting around in a doctor’s surgery waiting for something to happen. So more often than not, it is a process of elimination and pure luck that a doctor believes you when you say dairy was the culprit.
Dairy free trial
If you are breastfeeding then this is much easier to do as of course all you have to do is cut out dairy yourself. It is worth noting here that a soya allergy often goes hand by hand with dairy so it is worth cutting out both to ensure you are starting with a blank slate.
It may seem overwhelming but believe me, it is much easier than battling doctors for formula!
Obviously breastfeeding isn’t for everyone for a variety of reasons and so you may need to go to your doctor and request a dairy-free formula. If this is the case then you will have to explain the symptoms your baby has been exhibiting.
This is not the time to be doubting yourself – you are the voice for your baby so go in there with determination. There is still so little understanding (although it is much better than my first experiences in 2013) and so doctors will often assume you are a hysterical mother.
It sounds disgusting but if you can take in one of their mucousy nappies then that is proof of a digestive upset. Combined with the other symptoms you will list, the doctors will have a better understanding of what you are dealing with.
They will offer you the dairy free formula, which comes in the form of extensively hydrolyzed milk. This means that the proteins found in cow’s milk have been broken down in such a way that they won’t be recognized as a threat by the body anymore.
There are many types, some more broken down than others so don’t lose heart if one doesn’t work for your baby.
How long does it take for dairy to leave the system?
My own experience (from both breastfeeding and formula feeding my son and daughter respectively) is that the results were almost immediate. The day my daughter had her first bottle of formula she was so content and fell asleep.
I cried.
She hadn’t had a nap since she was 2 weeks old and we didn’t manage to get to the bottom of her issues until she was almost 8 weeks old.
It takes longer if you are breastfeeding because of course the dairy needs to leave your breastmilk as well as your baby’s system but still I found improvements within a day or so.
If you don’t notice any difference then you may want to explore other allergens in your own diet that could be triggering the reaction.
Reintroducing dairy
If you notice improvements and are breastfeeding then you may just want to carry on without conforming the allergy officially. Don’t rock the boat, I say.
If you do want to trial it then it is recommended to eat a yogurt and note the effects within 72 hours.
However, if you are under the doctor and are trialling a dairy free formula then they will most likely want you to trial some dairy and note the reaction. Keep a feed diary, noting down any changes in behaviour after the introduction of one bottle of dairy-based formula.
You will most likely notice a difference within an hour or so but keep a note of all behaviours within 72 hours.
If you don’t notice any symptoms returning then carry on the reintroduction of dairy, either through your diet or bottles. It could well be that they are suffering from lactose intolerance and the build-up of milk in their bodies is the cause of the issues.
My eldest suffered with Lactose intolerance and so I simply switched to Lacto-free products and later on when she took a bottle we used the reduced lactose formula on the market.
Trust your instincts.
Other useful posts
Our journey up the milk ladder
The story of my allergy babies [VIDEO]


Summer Haffner
Friday 8th of July 2022
Hi Katy, you mentioned that your child had a lactose problem. I’m curious at what age you figure this out? I was under the impression of infants who were exclusively breast-fed we’re almost never lactose intolerant, because human lactose is a normal component of breastmilk. ?
Katy
Monday 11th of July 2022
Hi Summer,
I think there is very little research into this field and therefore not much information to go by. I only have my own experience to go on so you may or may not find it helpful for your own situation. Grace was a very unsettled baby but 11 years ago the internet wasn't what it is now and all I had to go on was my mother and the health visitor telling me "all babies cry and are fussy". It was only when she reached 3 months and was STILL unsettled and fussy that I started to think their advice was a load of rubbish. Every day for 3 months she had green explosive poos - several changes of outfits a day. I did a tonne of research and realised lactose overload was the issue. Of course, we have lactose in our own milk, but as I was also drinking milk and eating dairy products, the cows lactose was entering my system and increasing the amount. As soon as I started eating lacto-free products she SLEPT! It was like a miracle. The explosive poos stopped and she was happy as a clam. When I weaned her, she had lacto-free products until around 18 months when her system seemed to be able to handle normal dairy again. She's never had a problem since. It's also important to make sure that when you are breastfeeding that you completely drain one side before switching as apparently the thinner fore milk is higher in lactose and so by making sure the baby gets the thicker hind milk you ensure the baby goes longer between feeds and doesn't get too much milk, too frequently - adding to the lactose overload. Hope that helps!