Blue breastmilk, is it antibodies?

What’s the deal with Blue breastmilk?

The image on the left above is a screenshot from a popular Facebook post showing the amazing change of colour in this mum’s breastmilk which, just like many other Facebook posts showing images of blue breastmilk, puts the change down to an increase in antibodies.

When you or your baby is fighting infection, the level of antibodies in your breastmilk increases, helping your baby to fight off any pathogens they have been exposed to. I’m sure we can all agree that this is pretty amazing, but does it make breastmilk turn blue? Probably not.
This image demonstrates antibodies in action. The ‘antigen’ is the foreign body your body is fighting against, such as a bacterium or virus. The top of the Y-shaped antigen takes on a specific shape in order to bind to the specific antigen it is targeting. Once it’s got hold of it, it will either neutralise it or destroy it, with the aid of a few other cells. When you breastfeed, you pass antibodies to your baby to help them combat specific pathogens in their environment.
Antibodies are tiny proteins in our blood, produced by white blood cells, which target specific pathogens and destroy or neutralise them. They don’t turn breastmilk blue, as far as anyone is aware.
Antibodies are found in much higher levels in colostrum than in mature milk, so if antibodies turned milk blue then why is colostrum generally a rich yellow/orange colour?
This image by Mamma Natural shows the typical yellow/orange colour of colostrum
Breastmilk has a natural bluish hue caused by the presence of casein (which accounts for 40% of the protein content in your milk). This blue hue is usually more visible when the volume of your milk is high and the fat content relatively lower. So what could cause that?
πŸ’™ Full breasts- Between feeds, some of the fat globules in your milk stick to each other and separate from the rest of the milk, sticking to the walls of your milk ducts. When your let down reflex is triggered at the beginning of a feed, the milk leaves some of its fat behind when it comes out. As the feed progresses, more and more of the fat left behind is washed from the walls of your milk ducts, so the fat content of your milk becomes gradually higher. More on that here. When it’s been a while since your last feed or your breasts are very full, more of the fat in your milk will be left behind at the start of the feed and, with less creamy fat, the blue hue of casein is more visible. This is often more noticeable when your expressed milk has been sat for a while, and the fat has separated and settled in a layer at the top of your milk.
πŸ’™ Hot weather- In very hot weather, the water content in your milk increases to help keep your baby hydrated, which is why breastfed babies do not need extra water in hot weather. The photo below shows my own breastmilk. Both bottles were expressed shortly before a feed when both me and my son were in good health, but the bottle on the right was expressed on a particularly hot day. The likelihood is that this milk appears blue because it has an increased water content.

πŸ’™ Illness- Lots of mums report that their milk appears blue when their baby is ill, and most put this down to antibodies. However, there is absolutely no evidence that this is the case. It is more likely that milk sometimes appears blue when babies are ill because of an increased water content or increased volume of milk caused by a change in your baby’s feeding pattern in response to their illness, rather than because of the increased antibodies.

Lots of women worry that their milk isn’t meeting their baby’s needs if it doesn’t change colour, or worry that their baby must be ill if their milk appears blue. The fact is, breastmilk is a live fluid, continually changing in response to lots of different factors to meet your baby’s needs. The composition of your milk subtly changes throughout each feed, according to the time of day, as your baby gets older and, as demonstrated by this post, in response to infection and even the weather! But these changes happen at a molecular level and are not always visible, so please don’t worry if your milk always seems the same colour- the changes are there, even if you can’t see them!


The colour of your breastmilk is generally nothing to worry about. The range of ‘normal’ when it comes to breastmilk colours is very wide, and unless you express then the likelihood is that you won’t even notice any changes! But if you are concerned about a change in your breastmilk, speak to someone trained in breastfeeding support.


Boobie Babies on Facebook

How Your Breasts Work

Am I making enough milk?

Foremilk vs Hindmilk: One less thing to worry about!

Expressing and Storing Breastmilk

The information on this page should not be used in place of medical advice. Information found online should always be discussed with your own IBCLC, Dr or Midwife to ensure it is appropriate for you and your baby’s situation. Contact your Dr, Midwife or Health Visitor with any concerns about your own or your baby’s health and welfare.

Disclaimer: The views, thoughts, and opinions expressed in the text on all pages of this website belong solely to the author, and do not necessarily reflect the views of the author’s employer, organization, committee or any other group or individual, unless explicitly stated otherwise.

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