A closer look at breast inflammation, fever, and use of anti-inflammatory medications

Inflammation is a vital part of your immune system's healthy function

Inflammation is the way your immune system cares for and protects your body, keeping the myriad different elements of your immune system in balance in ways that are usually invisible to you, so that your tissues remain healthy and resilient.

Inflammation both responds to, and is triggered by, a myriad of either up- or down-regulating feedback loops. These feedback loops act on various kinds of immune cells and clotting proteins, as well as upon networks of signalling molecules.

• Normal healthy inflammation inside our body cleans up debri from our own cell or macromolecule processes, often because they are damaged, such as in an arthritis, or in a lactating breast when a tiny milk gland breaks down, which happens all the time.

• Normal healthy inflammation removes those random or stray cells which might go rogue if they were to remain in our tissues.

• Inflammation also heals wounds in, or damage to, the integrity of, our skin and organs.

• An inflammatory response is launched in response to something coming in from outside our body, such as a foreign body or microbes.

Inflammation needs to be in balance and not overactive if we are to remain well

We need our bodies' ongoing and constant low-level inflammatory or wound healing processes, in our lactating breasts as well as throughout our bodies!

Inflammation is like the engine of the immune system, which needs to keep purring along, with intermittent flare-ups to neutralise immediate threats. This constant low level activity of the immune system inflammatory processes ensures homeostatic stability in dynamic tissues through myriad feedback loops.

The lactating breast is one of the most dynamic tissues in your body, characterised by constant healthy inflammatory surveillance and activity.

What is clinically relevant inflammation?

Once an inflammatory response has intensified in a localised part of the body, it is likely to become apparent clinically (that is, in a way that you feel or that causes health problems).

The five signs of acute inflammation in your body generally

1. Pain, which results when a build-up of fluid leads to swelling, and swollen tissues push against sensitive nerve endings.

2. Redness, which occurs when there is an increased blood flow to the area. This is how the inflammatory response brings in immune factors.

3. Heat, which is another result of this increased blood flow.

4. Swelling, which results from both the dilation of the tiny blood vessels in your tissues (capillaries and venules). Swelling is also a result of inflammatory factors defusing out through leaky walls of the capillaries into the surrounding tissue.

5. Loss of function, which occurs because of the impact of pain, redness, heat and swelling on bodily tissues. In the breast, this how inflammation can cause worsening cycles of tissue disruption.

Sometimes these signs aren’t present yet even though your body has begun to launch a vigorous inflammatory response. At other times, inflammation causes tiredness, unwell feelings, or fever. Inflammation also results in increased levels of biomarkers including C-reactive protein (CRP).

Inflammation can become severe and end-stage

• An area of focussed inflammation which doesn’t resolve might result in an abscess, which is the body’s way of walling off the area of infection and broken down tissue, and attempting to ensure it doesn’t continue to affect the rest of the body. The relationship between inflammation and infection is complex. An infection results when elements of the microbiome or an external organism overwhelm our immune system's healing inflammatory response.

• An abscess, if left untreated, gradually acts upon the overlying skin to damage it. 'Pointing' of the abscess results, and when the skin breaks down completely, pus from the abscess leaks to the outside world through a fistula.

Sometimes, acute inflammation can develop into a septicaemia, which is infection spreading throughout the whole of the body via the blood stream. Septicaemia was often fatal before the advent of antibiotics.

Fever is your immune system's helper

Fever may accompany your body's response to increasing inflammation. From the perspective of evolutionary biology, fever is crucial for immune system regulation and brings a survival advantage during illness. The high body temperatures of fever make certain proteins more active. These proteins then switch on the genes which activate the white cells, your immune system's powerful healing cells.

Too much use of medications to suppress fever stops fever positively activating your immune system. Fever is an ancient part of your immune response, and it's doing good.

It makes sense to use ibuprofen or paracetamol sometimes, to help you feel less sick and to sleep better. This intermittent use is quite different to the (inaccurate) advice that you must use anti-inflammatories regularly once you develop mastitis to stop the fever and treat the inflammation.

When do the normal, invisible inflammatory processes of a lactating breast become the problematic kind of breast inflammation?

Inflammation is a set of feedback loops designed to address the disruption and re-assert equilibrium.

• Neutrophils and macrophages are the first rapidly induced defense strategy.

• Chemical messengers such as cytokines and chemokines secreted by neutrophils and macrophages lead to the eradication of antigens.

The lactating breast is in a state of dynamic homeostasis. This means that the environment of your breasts is constantly changing. Your breasts' immune system has multiple feedback loops operating to keep them stable, constantly downregulating or upregulating small imbalances. The kind of breast inflammation which you can feel and see emerges when one or various feedback loops are out of balance.

Two main mechanisms interact together to cause a cascade of worsening inflammation: ductal occlusion, and worsening positive pressure within the glandular and ductal systems. Here are things it helps to know.

• Two-thirds of the glandular tissue of the lactating breast is found within a three-centimetre radius of the nipple base, and ultrasound imaging has shown that milk ducts are very easily compressed by light pressure, similar to the way light touch compresses the veins on the back of your hand. These ducts which are visible in a woman's breast tissue with imaging are the largest possible milk ducts. Imagine how easily the tiny branches are pressed shut, deeper within the breast!

• Ducts are not storage vessels. They lie empty and even squashed shut for some time after milk has been removed.

• Lactocytes constantly secrete milk into the alveolar lumens. A small amount of milk might also flow into and accumulate in the ducts, under the slightly positive pressure of milk secretion within the alveoli.

• Milk is removed from the breasts by the intermittent negative pressure of suckling and the intermittent positive pressure of milk ejection in the ductal system, working in tandem. Sometimes breasts leak milk in the absence of suckling, due to positive pressure of milk ejection, although in the absence of suckling some backflow of the milk in the ducts is also evident with milk ejection.

• Milk ejection results in contraction of alveoli and dilation of the ducts.

• Occlusion of the ducts in response to mechanical pressure from the outside interferes with the capacity of milk to be removed from areas of the breast because the duct is compressed, even when exposed to the negative pressure of suckling.

• If milk can’t be extracted from a duct, the cavity inside the gland into which the lactocytes secrete milk fills and become very dilated. This places the junctions between the lactocytes under severe mechanical stress, causing the release of inflammatory factors. An inflammatory cascade in the connective tissue or stroma surrounding the glandular tissue is triggered.

• The resultant dilated capillaries and swelling caused by the inflammation then further worsens ductal occlusion, which worsens milk back pressure and inflammation.

The fever of breast inflammation

Fever is an important part of our breasts' immune response to stress. When there is a lot of inflammation happening in one part of your breasts with a mastitis, or the whole of your breasts with engorgement, fever is activated. This doesn't mean you have an infection, although it does mean that you have active and acute inflammation, which requires a lot of attention and care from both others and yourself, so that it heals and doesn't keep worsening. Your body speaks to you through fever, because when you feel sick your body is telling you to stop, rest, have others care for you.

Stopping the fever doesn't help heal a visible, painful inflammation in the breast, despite what you might have heard. You can find out more about fever when you have mastitis or breast inflammation here. The research does clearly tell us that anti-inflammatory medications in general downregulate a tissue's healing inflammatory response, and that fever from an evolutionary biology perspective is essential for immune system regulation and helps recovery much of the time (- though this won't always be true).

This is why in the Neuroprotective Developmental Care approach to breast inflammation recommends taking anti-inflammatories as a backup when you're feeling awful, or at bedtimes to help you sleep, but not as a regular eight-hourly dose. More is not always better!

Recommended resources

PBL Foundations

Cold compresses and anti-inflammatory medications don't help resolve mastitis or breast inflammation

PBL Advanced

There is no research or biological rationale to support the belief that routine use of non-steroidal anti-inflammatories for mastitis 'treats the inflammation'

Breast stroma is a mechanically and hormonally sensitive microenvironment which facilitates mammary gland activity through wound-healing or inflammatory immune responses

The protective role of inflammation in the lactating breast: activation of milk microbiome, somatic cells, and fever

What does the research tell us about overuse of non-steroidal anti-inflammatories in mastitis?

Selected references

Douglas P. Re-thinking benign inflammation of the lactating breast: a mechanobiological model. Women's Health. 2022;18:17455065221075907.

Douglas PS. Re-thinking benign inflammation of the lactating breast: classification, prevention, and management. Women's Health. 2022;18:17455057221091349.

Evans SS, Repasky EA, Fisher DT. Fever and the thermal regulation of immunity: the immune system feels the heat. Nat Rev Immunol. 2015;15(6):335-349.

Geddes DT. The anatomy of the lactating breast: latest research and clinical implications. Infant. 2007;3(2):59-63.

Geddes DT. The use of ultrasound to identify milk ejection in women - tips and pitfalls. International Breastfeeding Journal. 2009;4(5):doi:10.1186/1746-4385-1184-1185.

Geddes DT, Gridneva Z, Perrella SL, Mitoulas LR, Kent JC, Stinson LF, et al. 25 years of research in human lactation: from discovery to translation. Nutrients. 2021;13:1307.

Harper CV, Woodcock DJ, Lam C. Temperature regulates NF-kB dynamics and function through timing of A20 transcription. The Proceedings of the National Academy of Sciences. 2018;115(22):E5243-E5249.

Ramsay DT, Kent JC, Hartmann RA, Hartmann PE. Anatomy of the lactating human breast redefined with ultrasound imaging. Journal of Anatomy. 2005;206:525-534.