It tends to arrive fast. One feed you're fine, a few hours later there's a hot, tender patch on one breast, and by evening you're shivering under a blanket in July feeling like you've been hit by a truck. That's mastitis, and it's far more common than anyone mentions before it happens to you.
It's also very treatable, especially caught early - which is the whole point of knowing what to look for before you're too foggy to Google it.
What it actually is
Mastitis is inflammation of breast tissue, usually triggered by a blocked milk duct that isn't clearing properly - milk backs up, the surrounding tissue becomes inflamed, and sometimes an infection develops on top of that. It's most common in the early weeks of breastfeeding but can turn up at any point, including well into an established feeding routine.
The tissue affected is often wedge-shaped, radiating out from the nipple, because that's the shape of a milk duct under pressure.
The signs, in the order they usually show up
- A firm, tender, often red patch on one breast - sometimes with a hard lump you can feel
- The area feels noticeably warmer than the rest of the breast
- Flu-like symptoms arriving quickly - chills, aching, fatigue
- A fever, often 38°C or higher, that seems to come from nowhere
- Pain that's worse on one side, sometimes sharp during a feed
What actually helps in the first 24 hours
- Keep feeding or expressing from the affected side regularly - stopping altogether tends to make it worse, not better
- Start feeds on the affected side when possible, when baby's suck is strongest
- Warmth before a feed can help milk flow; cold packs after a feed can ease pain and swelling
- Gentle massage toward the nipple during a feed, rather than aggressive kneading, which can worsen inflammation
- Rest as much as is physically possible - genuinely difficult with a newborn, but the body needs it here
When it needs more than home care
If a fever persists past 24 hours, symptoms worsen rather than ease, or there's visible pus or red streaking, it's time to see a GP - antibiotics are often needed once an infection has taken hold, and delaying doesn't make it resolve faster.
Recurrent mastitis is worth a proper look at latch and positioning with a lactation consultant, since an underlying feeding issue is often what's causing ducts to block in the first place.
The part that gets missed
Nobody tells you how suddenly it hits, or how much like the flu it can feel, which means the first time it happens most women assume they're just getting sick. If you're breastfeeding and the flu arrives alongside a sore red patch on one side, mastitis is worth considering before anything else.
Caught early and treated properly, it usually clears within a few days. It is unpleasant, not dangerous, and not a sign you're doing anything wrong.