Mastitis: Symptoms, Types, Causes and Treatment

Mastitis is a prevalent and often painful condition affecting the mammary glands, with significant impacts on both human health and animal agriculture. For breastfeeding women, it can disrupt feeding and quality of life, while in dairy animals, mastitis is a major cause of economic loss due to reduced milk yield and quality. Understanding mastitis—its symptoms, types, underlying causes, and available treatments—is crucial for prompt recognition and effective management, ensuring better outcomes for both patients and livestock. This article explores the condition in detail, synthesizing the latest research for a clear and practical overview.

Symptoms of Mastitis

Mastitis often announces itself loudly. Whether in humans or animals, the hallmark symptoms are unmistakable and can escalate quickly if not addressed. Recognizing these signs early is key to preventing complications such as abscess formation or chronic inflammation.

Symptom	Description	Common In	Sources
Redness	Localized erythema	Humans, Animals	1 2 4
Swelling	Breast/gland enlargement	Humans, Animals	2 4 7
Pain/Tenderness	Discomfort to touch	Humans, Animals	1 2 4
Warmth	Increased local temperature	Humans, Animals	1 2
Lump/Mass	Palpable mass, sometimes hard	Humans	6 15
Fever	Systemic temperature elevation	Humans, Animals	2 4
Flu-like symptoms	Malaise, chills, fatigue	Humans	4 15
Decreased milk	Reduced milk yield or altered milk quality	Humans, Animals	7 9 15

Table 1: Key Symptoms

Core Clinical Features

The classic triad of mastitis includes redness, heat, and pain in the affected breast or gland. Swelling is common and often accompanied by a sensation of heaviness or firmness. In more advanced cases, the tissue may feel hard or lumpy due to abscess formation or significant inflammation 1 2 4 6.

Systemic Symptoms

Fever and flu-like symptoms such as chills, malaise, and fatigue may accompany local breast changes, especially in infectious mastitis. These systemic signs suggest that the inflammation is severe or that infection has spread beyond the local tissue 2 4 15.

Functional Impact

One of the most significant consequences of mastitis, particularly in lactating women and dairy animals, is a reduction in milk production. The milk itself may also change in color, consistency, or taste, and, in severe cases, may contain pus or blood 7 9 15.

When to Seek Help

Prompt medical or veterinary attention is recommended if symptoms escalate rapidly, if an abscess is suspected (a localized, fluctuant lump), or if there is no improvement with initial management. Early intervention can prevent chronic complications and improve recovery.

Types of Mastitis

Mastitis is not a one-size-fits-all condition. It encompasses a range of subtypes, each with distinct causes, presentations, and management strategies. Understanding these types is crucial for tailored treatment and avoiding misdiagnosis, such as confusing mastitis with breast cancer.

Type	Key Features	Typical Patient/Animal	Sources
Lactational	During/after breastfeeding	Women, dairy animals	4 9 15
Non-lactational	Not related to lactation	Women (non-breastfeeding), men	4 9
Acute Infectious	Rapid onset, often bacterial	All species	2 11 15
Chronic	Persistent/recurrent, less severe	All species	4 11
Abscess-associated	Collection of pus	Humans, animals	2 6
Granulomatous	Non-caseating granulomas, mimics cancer	Humans	3 5 6
Autoimmune	Immune-mediated, often part of systemic disease	Humans	5 6
Cancer-related	Inflammation linked to malignancy	Humans	1 4

Table 2: Types of Mastitis

Lactational Mastitis

The most common form in women and dairy animals, lactational mastitis typically occurs during breastfeeding or peak lactation. It is usually caused by milk stasis and secondary bacterial infection, but can also be non-infectious 4 9 15.

Non-lactational Mastitis

This type affects individuals outside the context of lactation, including non-breastfeeding women and, rarely, men. It may be due to infection, autoimmune disease, or ductal disease 4 9.

Infectious vs. Non-infectious

• Acute Infectious Mastitis: Characterized by sudden onset, marked redness, heat, and pain, often due to bacterial pathogens such as Staphylococcus aureus 2 11 15.
• Non-infectious or Autoimmune Mastitis: Includes idiopathic granulomatous mastitis and other immune-mediated forms, often requiring immunosuppressive therapy 5 6.

Chronic and Abscess-associated Mastitis

Chronic mastitis features less intense but persistent symptoms. Abscess formation is a complication of both acute and chronic mastitis and presents as a localized, fluctuant mass, sometimes requiring drainage 2 6.

Granulomatous and Cancer-related Mastitis

Granulomatous mastitis can closely mimic breast cancer, presenting with a firm mass and requiring biopsy for definitive diagnosis 3 5 6. Cancer-related mastitis is less common but critical to identify, as it reflects underlying malignancy with an inflammatory component 1 4.

Causes of Mastitis

Mastitis arises from a complex interplay of microbial, immune, and environmental factors. While infection is a leading cause, non-infectious triggers and systemic conditions also contribute, especially in chronic and atypical cases.

Cause	Mechanism/Trigger	Prevalence/Context	Sources
Bacterial infection	Pathogen invades mammary tissue	Common, esp. lactational	2 7 11 15
Milk stasis	Blocked ducts, incomplete drainage	Breastfeeding women, dairy animals	6 9 15
Autoimmune reaction	Immune attack on breast tissue	Rare, often with systemic disease	5 6
Ductal disease	Duct ectasia, periductal inflammation	Non-lactational women	4 5
Malignancy	Tumor-associated inflammation	Rare but serious	1 4
Microbiome dysbiosis	Gut or breast microbial imbalance	Emerging evidence	8 10 15
Trauma	Physical injury to breast/udder	Occasional	4 7

Table 3: Major Causes of Mastitis

Infectious Causes

Most cases of mastitis, particularly those that are acute, result from bacterial infection. The most common culprits are Staphylococcus aureus, Staphylococcus epidermidis, and corynebacteria 2 7 11 15. These organisms can enter through cracks in the nipple or teat, or via retrograde movement up the ductal system.

Non-Infectious and Immune-Mediated Causes

Non-infectious mastitis includes conditions like idiopathic granulomatous mastitis, which is thought to have an autoimmune basis and often presents similarly to infection or even cancer 5 6. Other autoimmune diseases, such as lupus or thyroiditis, can also involve the breast 5.

Milk Stasis and Ductal Disease

Milk stasis—when milk is not adequately removed from the breast—creates an environment for bacterial growth and inflammation. Ductal ectasia (widening of the ducts) and periductal inflammation are more common in non-lactational mastitis 6 9 15.

Microbiome and Systemic Factors

Recent research highlights the role of the microbiome, both in the breast and the gut, in mastitis pathogenesis. Dysbiosis, or an imbalance in microbial communities, can trigger or exacerbate inflammation, even in the absence of overt infection 8 10 15. In animals, gut-derived endotoxemia and systemic inflammation have been shown to induce or worsen mastitis 10.

Malignancy and Trauma

Rarely, mastitis may be the result of underlying breast cancer, especially inflammatory breast cancer, or from direct trauma to the breast or udder 1 4 7.

Treatment of Mastitis

Timely and appropriate treatment of mastitis is crucial to relieve symptoms, prevent complications, and, in the case of dairy animals, restore milk production. Treatment approaches vary depending on the underlying cause, severity, and whether the patient is human or animal.

Approach	Description	Indications	Sources
Antibiotics	Oral or topical antimicrobials	Infectious cases	2 7 12 13 15 16
Drainage/Aspiration	Removal of pus or fluid	Abscesses	2 6
Anti-inflammatories	NSAIDs, steroids, immune modulators	Immune-mediated, severe cases	5 6 13
Supportive care	Rest, hydration, continued breastfeeding/milking	All cases	4 15
Probiotics	Restore healthy microbiome	Adjunct/alternative	8 14 15
Surgery	Rare, last resort for refractory cases	Complicated abscess, poor healing	6
Alternative therapies	Herbal, plant-based treatments	Veterinary, adjunct	14

Table 4: Treatment Modalities

Antibiotic Therapy

For acute infectious mastitis, especially in lactating women and dairy animals, antibiotics are the mainstay of treatment. Empiric therapy usually targets Staphylococcus species, with adjustments based on culture results or response 2 12 13 15 16. In animals, intramammary infusion is common, but concerns about antibiotic resistance and residues drive the search for alternatives 12 14.

Abscess Management

If an abscess develops, it may require percutaneous drainage or aspiration, often under ultrasound guidance. Larger or refractory abscesses may need repeated procedures or, rarely, surgical intervention 2 6.

Anti-Inflammatory and Immunosuppressive Therapies

Non-infectious, autoimmune, or granulomatous mastitis may respond better to steroids or immune modulators (e.g., methotrexate) than antibiotics. Topical and intralesional steroids are increasingly used in idiopathic granulomatous mastitis, with good outcomes and fewer side effects compared to oral steroids 5 6 13.

Supportive and Adjunctive Measures

• Continued Milk Removal: Whether breastfeeding or milking, continued emptying of the breast or udder helps resolve milk stasis and prevent worsening infection 4 15.
• Pain Relief and Hydration: NSAIDs or other pain relievers, along with adequate fluids and rest, support recovery 5 6 13.
• Probiotics: Modulating the microbiome with probiotics shows promise as both a preventive and therapeutic strategy, especially where dysbiosis or recurrent mastitis is an issue 8 14 15.

Alternative and Emerging Therapies

Especially in veterinary settings, herbal and plant-based treatments are gaining interest as alternatives to antibiotics. These may offer antimicrobial effects and reduce reliance on traditional drugs, but more research is needed to confirm efficacy and safety 14.

Surgical Intervention

Surgery is rarely needed but may be considered in cases of persistent abscess, extensive tissue damage, or non-resolving disease after medical management 6.

Conclusion

Mastitis remains a complex and significant health issue, with wide-ranging impacts in both human healthcare and animal husbandry. Understanding its symptoms, subtypes, causes, and treatments ensures prompt and effective intervention. Key takeaways include:

• Classic symptoms are redness, heat, pain, swelling, and sometimes systemic illness.
• Types of mastitis range from lactational and acute infectious to autoimmune and cancer-related forms, each requiring tailored management.
• Causes include bacterial infection, milk stasis, immune dysfunction, ductal disease, trauma, cancer, and increasingly recognized roles for the microbiome.
• Treatment must be individualized—antibiotics for infection, drainage for abscess, immunosuppressives for autoimmune forms, and supportive care throughout.
• Emerging alternatives like probiotics and plant-based therapies may help reduce antibiotic reliance and improve outcomes.

By staying informed and vigilant, clinicians, veterinarians, and patients can work together to ensure timely diagnosis and optimal recovery from mastitis.