Mastitis
Symptoms, Causes & Treatment
Understanding mastitis: what causes it, how to recognise it, and the effective antibiotic treatments available to breastfeeding women online.
What Is Mastitis?
Mastitis is inflammation of the breast tissue that may or may not involve bacterial infection. It most commonly occurs in women who are breastfeeding (lactational mastitis), typically within the first six weeks after delivery, but can occur at any stage of breastfeeding. Non-lactational mastitis can also occur in women who are not breastfeeding and, rarely, in men.
Lactational mastitis affects approximately 1 in 10 breastfeeding women. It usually develops when milk stasis (a build-up of milk in the breast) occurs -- due to a blocked duct, infrequent feeding, or poor latch -- creating an environment in which bacteria can multiply. The most common causative organism is Staphylococcus aureus, which typically enters through cracked or damaged nipples.
Mastitis can range from a mild, localised area of breast tenderness with redness and warmth, to a severe, systemic infection with high fever, rigors, and the potential to develop a breast abscess. Prompt treatment -- continued breastfeeding or expressing, pain relief, and antibiotics when indicated -- usually resolves the condition quickly.
Importantly, breastfeeding should almost always continue during mastitis. Stopping breastfeeding can worsen milk stasis and prolong the infection.
What Are the Symptoms of Mastitis?
Mastitis symptoms develop rapidly and combine local breast symptoms with systemic illness.
Mastitis: breast pain, redness, warmth, and swelling · Fever and flu-like symptoms · Hard, red, hot area of breast · Nipple discharge (may be pus) · One breast typically affected · Symptoms may develop rapidly over hours
Abscess formation (fluctuant swelling, very tender) · Sepsis signs: high fever >39°C, rigors, confusion · Failure to improve after 48 hours of antibiotics · Mastitis in a non-breastfeeding woman (requires investigation to exclude inflammatory breast cancer)
Seek same-day emergency assessment if mastitis symptoms are rapidly worsening despite antibiotic treatment, if you develop a fluctuant breast lump suggesting abscess, or if you have high fever with rigors suggesting sepsis.
What Causes Mastitis?
Mastitis results from a combination of milk stasis and bacterial infection. Understanding the cause helps identify how to prevent future episodes.
Lactational mastitis occurs when milk stasis allows bacteria (usually Staph aureus) to multiply in breast tissue. Incomplete breast emptying, engorgement, and nipple cracks are the primary drivers.
Non-lactational mastitis occurs in non-pregnant women and men. Causes include periductal mastitis (smoking-related), idiopathic granulomatous mastitis, and rarely inflammatory breast cancer — which must always be excluded.
Recurrent mastitis may indicate ductal abnormality, blocked lactiferous duct, or an underlying immunological condition. Recurrent non-puerperal mastitis warrants imaging (ultrasound ± mammogram) to exclude malignancy.
Contact dermatitis occurs when skin comes into contact with an irritant (irritant contact dermatitis) or a specific allergen (allergic contact dermatitis via type IV delayed hypersensitivity). Common allergens: nickel, latex, fragrances, preservatives.
Common eczema triggers include wool, synthetic fabrics, dust mites, pet dander, pollen, mould, soaps, detergents, food allergens (in children), and emotional stress. Identifying and avoiding personal triggers reduces flare frequency.
Psoriasis is an immune-mediated chronic inflammatory skin disease. T-cell activation drives rapid keratinocyte proliferation (3–5 days instead of 28–30), producing the characteristic thickened plaques.
Key Risk Factors
How Is Mastitis Diagnosed?
Mastitis is diagnosed clinically on symptoms and examination. Breast milk culture is performed if mastitis does not respond to first-line antibiotics. Ultrasound is used to investigate for abscess if a fluctuant lump is present.
How Is Mastitis Treated?
Antibiotics are the cornerstone of mastitis treatment. Breastfeeding or expressing must continue throughout treatment.
Supportive Measures
Continue feeding or expressing from the affected breast frequently. Massage toward the nipple to help clear blocked ducts. Apply warm compresses before feeding. Take ibuprofen and paracetamol for pain and fever. Rest as much as possible.
Recurrent Mastitis
Recurrent mastitis may indicate persistent poor latch, incomplete drainage, or Staphylococcus aureus nasal carriage. Lactation support is essential. More than two episodes warrants investigation for underlying breast pathology.
When Should You Seek Medical Advice for Mastitis?
Rapidly worsening symptoms despite antibiotics · Fluctuant (fluid-filled) lump suggesting abscess requiring drainage · High fever with rigors and confusion suggesting sepsis.
You have breast redness, warmth, and pain with fever · You have a blocked duct that has not resolved after 24 hours of frequent feeding · You have had a previous breast abscess.
How Can You Prevent Mastitis?
Most mastitis is preventable with good breastfeeding technique and prompt management of early warning signs.
Frequent, effective milk removal is the most important mastitis prevention. Feed or express every 2–3 hours; never skip feeds. Get breastfeeding support from a midwife, health visitor, or lactation consultant early — before problems develop.
Ensure your baby latches on deeply and correctly. A poor latch causes nipple trauma (cracks), which are an entry point for bacteria. Ask for a latch assessment if breastfeeding is painful.
Seek breastfeeding support immediately if you notice breast hardness, redness, or pain. Early identification and treatment of blocked ducts prevents progression to mastitis and abscess.
SPF 30+ sunscreen daily is the single most effective measure against all types of hyperpigmentation, including melasma, PIH, and solar lentigines. UV exposure stimulates melanin even on cloudy days. Apply year-round to face and neck.
Use a gentle, fragrance-free cleanser twice daily. Avoid scrubbing, which damages the skin barrier and worsens acne. Do not pick or squeeze spots — this increases scarring and prolongs healing time.
Start with gentle, consistent moisturising before escalating to active treatments. Over-the-counter benzoyl peroxide (2.5–5%) and adapalene 0.1% (Differin) are effective for mild acne without a prescription.
Speak to a Clinician About Mastitis
Through The GP Service, a licensed clinician can assess mastitis symptoms and prescribe appropriate antibiotic treatment quickly — without waiting for a GP appointment.
Expert clinical advice, when you need it.
Mastitis FAQs
Yes. Continuing to breastfeed or express milk is an important part of mastitis treatment. Stopping abruptly can worsen engorgement and infection. Antibiotics are safe during breastfeeding and most cases resolve fully with treatment.
Most women notice improvement within 24–48 hours of starting antibiotics. If symptoms are not improving after 48 hours or are worsening, return to your clinician — an abscess may have formed requiring drainage.
If untreated or inadequately treated, mastitis can develop into a breast abscess, which requires surgical drainage. This is why prompt antibiotic treatment is essential.
No. Mastitis is usually caused by milk stasis and bacterial entry through cracked nipples. It is not related to hygiene practices and should never make a woman feel responsible for her condition.
Flucloxacillin is the first-line antibiotic for mastitis in the UK. For penicillin-allergic women, erythromycin or clarithromycin is used. Your clinician will prescribe the appropriate agent based on your medical history.
Yes, mastitis can recur, particularly if the underlying cause (poor latch, blocked ducts, nipple damage) is not addressed. Lactation support from a midwife or breastfeeding specialist significantly reduces recurrence risk.
Ibuprofen is the preferred pain relief for mastitis as it also reduces inflammation. Paracetamol can be added for additional pain control. Both are safe during breastfeeding at standard doses.
For uncomplicated mastitis, a same-day or next-day GP appointment is appropriate. Attend A&E if you develop high fever with rigors, rapidly worsening redness, or signs of sepsis.