Causes of Mastitis
The causes of mastitis vary depending on whether the condition is lactational or non-lactational, but they all share one common issue: inflammation of the breast tissue. The main causes include milk stasis, bacterial infections, and trauma. Understanding these underlying triggers is essential for preventing recurrence, reducing severity, and improving outcomes. Although mastitis primarily affects breastfeeding women, it can also occur in others due to various medical or lifestyle factors.
Understanding the Underlying Mechanisms
The breast is a complex structure made up of lobules (milk-producing glands), ducts (milk-carrying channels), and connective tissue. Any part of this system can become inflamed, leading to mastitis. Typically, the process starts with milk stasis, where milk isn’t fully drained from the breast. This stagnant milk becomes a breeding ground for bacteria, which leads to infection and inflammation.
In non-lactational cases, inflammation may result from blocked ducts, trauma, or chronic conditions like diabetes or smoking-related damage.
1. Milk Stasis (Blocked Ducts)
Milk stasis is the most common cause of mastitis in breastfeeding women. It happens when milk builds up in the breast because it isn’t emptied completely during feeds. Some contributing factors include:
- Infrequent breastfeeding
- Poor latch or ineffective sucking
- Missed feeds or abrupt weaning
- Oversupply of milk
- Pressure from tight bras or baby carriers
As milk accumulates, it increases pressure within the breast and reduces blood flow. This impairs the immune response, creating an environment where bacteria can grow.
2. Bacterial Infection
Once milk stasis occurs, bacteria can easily enter. The most common bacteria responsible for mastitis are:
- Staphylococcus aureus
- Streptococcus pyogenes
- Escherichia coli
These bacteria usually enter through cracks or abrasions on the nipple. Damaged skin allows bacteria from the baby’s mouth or the mother’s skin to enter the milk ducts. Once inside, the bacteria multiply, causing the inflammation that leads to mastitis. This is infectious mastitis, which often requires antibiotics to treat.
3. Cracked or Damaged Nipples
Cracked nipples contribute to mastitis. They act as entry points for bacteria and can cause pain during feeding, leading to incomplete milk drainage. This worsens the likelihood of infection.
Nipple trauma may happen due to:
- Poor breastfeeding technique
- Improper latch by the baby
- Use of abrasive breast pads or rough fabrics
- Fungal infections like thrush, which weaken the skin
4. Weaning or Missed Feeds
Sudden changes in feeding frequency, like returning to work or reducing night feeds, can cause milk to accumulate and ducts to become blocked. When breasts stay full for too long, they can become engorged, which sets the stage for inflammation and infection.
Some mothers mistakenly reduce feeding because of nipple pain, which worsens the issue. Gradual weaning and proper breast-emptying techniques can help prevent this problem.
5. Smoking and Periductal Mastitis
For non-lactating women, periductal mastitis is often linked to cigarette smoking. Chemicals in cigarettes can damage the milk ducts and surrounding tissue, causing chronic inflammation and scarring.
This condition tends to affect women aged 30 to 50 and can sometimes look like breast cancer. Infections can occur repeatedly, and in severe cases, may lead to abscesses that need surgical intervention.
6. Immune Suppression and Underlying Illnesses
Women with weakened immune systems are more vulnerable to mastitis. Their ability to fight infections is reduced. Contributing factors include:
- Diabetes
- HIV/AIDS
- Chemotherapy or long-term steroid use
- Chronic fatigue or autoimmune disorders
In these cases, infections can spread quickly and may even become recurrent. A full health evaluation is important when mastitis occurs outside the typical breastfeeding period.
7. Breast Trauma
Direct injuries to the breast can lead to inflammation and even fat necrosis, which may resemble mastitis. Trauma can result from:
- Accidental knocks or falls
- Sports injuries
- Incorrect use of breast pumps
- Surgical procedures (e.g., biopsies or breast augmentation)
While less common, trauma-induced mastitis can be painful and may lead to fluid buildup, requiring drainage and antibiotics.
8. Retained Milk After Weaning
Even after weaning, milk production may continue. If this residual milk isn’t managed properly, it can cause engorgement and inflammation. This is especially likely if the weaning process was sudden or unplanned.
In rare cases, residual milk ducts may become infected months after weaning, requiring treatment with antibiotics or, in some cases, surgical drainage.
9. Obesity and Poor Hygiene
Obesity and poor hygiene can create an environment ideal for bacterial growth, which can lead to mastitis. Bacteria such as Staphylococcus epidermidis may grow on the skin and enter small cracks or lesions on the nipple.
Other risk factors include:
- Using unclean breast pumps
- Not changing breast pads frequently
- Wearing the same nursing bra for long periods
Maintaining good hygiene and allowing the skin to breathe can significantly reduce the risk of mastitis.
10. Hormonal Fluctuations
Hormonal changes during pregnancy, the menstrual cycle, or perimenopause may increase breast tissue density and susceptibility to inflammation. Although these shifts aren’t direct causes of mastitis, they may make certain individuals more likely to experience breast pain, tenderness, or mastitis-like symptoms.
It’s important to differentiate these from true infections to avoid unnecessary antibiotic treatment.
Summary
In summary, the causes of mastitis include a mix of physical, bacterial, lifestyle, and hormonal factors. Milk stasis, infections, nipple trauma, smoking, and immune suppression all play major roles in the development of this condition. Identifying and addressing these triggers early can help prevent recurrence and ensure effective treatment. Preventive strategies should focus on proper breastfeeding techniques, good hygiene, gradual weaning, and quick intervention when symptoms first appear.
