Mastitis and breast abscess

What these conditions are

Mastitis is inflammation of the breast tissue. It causes a red, warm, painful area, often accompanied by feeling unwell with fever or flu-like symptoms. Mastitis is most often associated with breastfeeding (lactational mastitis), but a separate non-lactational pattern affects women at other times in life and is more variable in presentation.

A breast abscess is a localised collection of pus that has formed when mastitis has not settled with antibiotics, or when an infected area has been left untreated. Abscesses present as a tender, fluctuant lump within an inflamed area; on ultrasound they appear as a fluid-filled cavity with debris.

Both conditions are common, and both are well treated when picked up early. The principle of treatment is prompt antibiotics, ultrasound to confirm whether an abscess has formed, and ultrasound-guided drainage if it has — surgical drainage in an operating theatre is rarely needed in modern practice.

Lactational mastitis and abscess

Mastitis during breastfeeding is common — affecting around one in ten to one in six breastfeeding women in UK studies. The usual cause is a combination of milk stasis (a blocked duct, or incomplete breast emptying) and bacteria entering through the nipple, leading to inflammation and infection of an area of breast tissue.

Symptoms typically include:

• A red, warm, painful area in the breast — often a wedge-shaped patch on one side.
• Pain on feeding from the affected side, sometimes with reduced flow.
• Flu-like symptoms — fever, chills, body aches, fatigue.
• A tender lump within the inflamed area, sometimes growing over a day or two.

First-line management is:

• Continue breastfeeding from the affected breast — emptying the breast helps clear the inflammation. Stopping breastfeeding makes mastitis worse, not better.
• Antibiotics to cover the bacteria typically involved — usually a 10–14 day course of flucloxacillin or a suitable alternative for penicillin-allergic patients. Most cases improve within 48 hours of starting antibiotics.
• Pain relief — paracetamol and ibuprofen are safe in breastfeeding and are usually sufficient.
• Warm compresses before feeding and gentle massage to encourage milk flow.
• A well-fitted bra — neither too tight (which restricts flow) nor too loose (which gives no support).

When to escalate:

• Symptoms not improving 48 hours after starting antibiotics.
• A persistent lump within the inflamed area, particularly one that feels fluctuant.
• Increasing pain despite treatment.
• Fever and unwellness escalating.

In any of these situations, an ultrasound is the next step — to look for an abscess that has formed under the area of inflammation. If an abscess is confirmed, the management changes from “antibiotics alone” to “antibiotics plus drainage”.

Non-lactational mastitis and abscess

Mastitis outside of breastfeeding is less common but still seen frequently. The causes are different:

• Periductal mastitis — inflammation around the major ducts behind the nipple, often associated with smoking. Can become recurrent and difficult to clear, and is sometimes associated with mammary duct fistula (a small connection between an inflamed duct and the skin).
• Skin infections of the breast, particularly in the inframammary fold or armpit.
• Sebaceous cysts that have become inflamed.
• Granulomatous (idiopathic) mastitis — a non-infective inflammatory condition that can mimic infection and typically does not settle with antibiotics; diagnosed on biopsy.
• Unusual organisms (such as TB or actinomyces) — uncommon in the UK but worth considering in patients from regions where these are more common, or when the picture is atypical.
• Inflammatory breast cancer — a rare but important diagnosis. An area of redness and inflammation that does not settle as expected on antibiotics needs prompt imaging and biopsy to exclude this presentation, even when infection seems the more likely cause.

The management of non-lactational mastitis is similar — antibiotics with broader cover than lactational mastitis — commonly co-amoxiclav, or a macrolide with metronidazole if penicillin-allergic — because non-lactational infection often involves anaerobic bacteria. Ultrasound to look for an abscess, and drainage if an abscess is present. Recurrent or persistent non-lactational mastitis sometimes needs a more involved approach (see below).

How an abscess is treated

The standard treatment for a breast abscess is ultrasound-guided needle aspiration combined with antibiotics. Surgical incision and drainage in an operating theatre is now rare in modern practice and is reserved for abscesses that cannot be controlled by aspiration.

What the procedure involves:

1. Local anaesthetic is injected into the skin over the abscess.
2. A needle (or small flexible cannula) is passed through the skin into the abscess under ultrasound guidance.
3. The pus is aspirated out into a syringe; the cavity is gently flushed with saline if needed.
4. A sample of the pus is sent to the laboratory to identify the bacteria and confirm antibiotic sensitivity.
5. The needle is withdrawn and a small dressing applied.

The whole procedure usually takes 10–15 minutes. The patient leaves the clinic the same day with the abscess decompressed.

Repeated aspirations are often needed — every few days at first, then less often as the cavity heals from the inside. Most abscesses settle over 2–4 weeks of repeated aspiration plus antibiotics. The schedule is tailored to your individual abscess.

When surgery is needed

A small minority of abscesses do need surgical drainage:

• Very large abscesses that cannot be effectively decompressed with a needle.
• Abscesses with thick, loculated pus that does not aspirate freely.
• Abscesses that recur or persist despite repeated aspiration and antibiotics.
• Recurrent periductal mastitis with associated abscess and fistula formation — sometimes treated with excision of the affected ducts (a form of major duct excision) once the acute infection has settled.

Where surgery is needed, it is usually a small day-case operation under general anaesthetic. The cavity is opened, the pus is drained, the cavity is irrigated, and the wound is either closed with a small drain or — for larger abscesses — left open to heal from the bottom up over 2–3 weeks of dressings.

Same-day pathway at the practice

For most patients with mastitis or a suspected abscess, the practice can usually arrange:

• A same-day or next-day clinic appointment for examination.
• Ultrasound at the same visit to confirm whether mastitis has progressed to an abscess.
• Aspiration at the same visit if an abscess is present.
• A prescription for antibiotics, sent directly or by email to your nominated pharmacy.
• A clear plan for the next 48 hours and a return visit if needed.

This rapid pathway is important because mastitis untreated for several days is more likely to progress to an abscess, and abscesses that have been present for more than a couple of weeks are harder to treat with aspiration alone.

For breastfeeding patients in particular, getting seen quickly avoids unnecessary disruption to feeding and the risk of needing to stop temporarily.

When to seek urgent care

⚠ A breast that is becoming increasingly red, hot, or swollen, especially with rising fever or feeling very unwell, needs prompt assessment — same-day or out-of-hours rather than waiting for a routine appointment. Untreated breast infection can occasionally progress quickly. If the practice cannot see you the same day, contact your GP or NHS 111 (in the UK) rather than waiting.

Related: Non-cancerous breast conditions · Breast pain assessment · One-stop breast clinic · Fees and insurance