Clogged Duct vs Mastitis: How to Tell the Difference (and When It's an Emergency)

It's 2 AM. You feel a hard, painful lump in your breast. Your first thought: clogged duct. But how do you know it's not something more serious — like mastitis?

As a nurse and IBCLC with nearly 30 years of experience, I've seen hundreds of moms confuse these two conditions. Getting it right matters because the treatment is different, and waiting too long with mastitis can lead to complications.

What is a clogged duct?

A clogged duct (also called a plugged duct) is a blockage in one of the milk ducts. It happens when milk isn't draining fully from a specific area of the breast.

Signs of a clogged duct:

• A hard, tender lump in one specific spot
• Pain that's localized to that area
• No fever (or only a very mild temperature)
• No body aches or flu-like symptoms
• The skin over the lump may be slightly pink or warm, but not bright red and spreading

A clogged duct is uncomfortable, but it's not an infection. With the right care — ice, rest, gentle hand expression, and fixing the latch — most clogs resolve within 24–48 hours.

What is mastitis?

Mastitis is an infection of the breast tissue. It often starts as a clogged duct that doesn't resolve, allowing bacteria to grow in the backed-up milk.

Signs of mastitis:

• Fever over 101°F (38.3°C) — this is the key differentiator
• Flu-like symptoms: body aches, chills, fatigue, headache
• A wedge-shaped or spreading area of redness on the breast
• The breast feels hot to the touch
• General feeling of being unwell, like you're coming down with the flu

Mastitis requires medical attention. Your doctor may prescribe antibiotics, and it's important to start them promptly. Continuing to feed or pump from the affected breast is safe and helps clear the infection.

The key differences at a glance

What to do if you think it's a clogged duct

The 2022 Academy of Breastfeeding Medicine (ABM) Protocol #36 recommends the BAIT method:

• B — Rest your body (skip a pump session if possible)
• A — Anti-inflammatory (ibuprofen 400–800 mg with food, if safe for you)
• I — Ice for 15 minutes between feeds (not heat!)
• T — Time and gentle hand expression toward the nipple

Continue feeding on the affected side. Make sure your baby has a deep, asymmetrical latch. If you're pumping, check that your flange size is correct — a wrong fit is a common hidden cause of recurring clogs.

What to do if you think it's mastitis

Contact your doctor or midwife today. Mastitis can progress quickly, and antibiotics may be needed. In the meantime:

• Continue feeding or pumping from the affected breast — this helps drain the infection
• Rest as much as possible
• Stay hydrated
• Use ibuprofen for pain and fever (if safe for you)
• Apply a cool compress for comfort

Don't wait to see if it gets better on its own. If you have a fever over 101°F, that's your signal to seek medical care.

When it's an emergency

Go to urgent care or the ER if you have:

• A fever that won't come down with medication
• Rapidly spreading redness
• Severe pain that makes it impossible to feed
• Discharge of pus from the nipple
• A hard, red area that feels like it's getting bigger by the hour
• Confusion, dizziness, or feeling very unwell

These can be signs of an abscess or severe infection that needs immediate treatment.

Preventing clogs from becoming mastitis

The best treatment is prevention. Here's what reduces your risk:

• Don't skip feedings or pump sessions — regular milk removal prevents backup
• Vary your feeding positions — different positions drain different areas of the breast
• Check your flange size — most pumps ship with a 24mm flange, which doesn't fit everyone
• Avoid tight clothing or underwire bras — pressure can block ducts
• Address stress and fatigue — stress tenses the muscles around ducts and inhibits let-down
• Get help early — if a clog doesn't start improving in 24 hours, see an IBCLC

If you're in Central Oregon and dealing with recurring clogs or a current one that won't budge, I can help. I'll assess your latch, check your pumping setup, and give you a personalized plan. Clogged duct care in Bend, OR →

Need personalized help?

Every feeding situation is different. If you're in Central Oregon or anywhere in the US, Willow can help — in-home or virtual.

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