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Blocked Ducts and Mastitis


Mastitis is a bacterial infection of the breast which usually occurs in breastfeeding mothers. However, it can occur even in women who are not breastfeeding or pregnant, and can even occur in small babies. Nobody knows exactly why some women get mastitis and others do not. Bacteria may gain access to the breast through a crack or sore in the nipple, but women without sore nipples also get mastitis.

Mastitis needs to be differentiated from a plugged or blocked duct, because the latter does not need to be treated with antibiotics, whereas mastitis often, but not always, does require treatment with antibiotics. A plugged duct presents as a painful, swollen, firm mass in the breast, often with overlying reddening of the skin, similar to mastitis, though not usually as intense. Mastitis, though, is usually associated with fever and more intense pain and redness of the breast. As you can imagine, it is not always easy to differentiate a mild mastitis from a severe blocked duct. A blocked duct can lead to mastitis.

In order to make a diagnosis of mastitis, there must be an area of hardness, pain, redness and swelling in the breast. The absence of such an area in the breast means that the mother does not have mastitis. Flu-like symptoms or fever alone are not enough to make the diagnosis of mastitis. Shooting pains in the breast without an area of hardness are not mastitis. These are more likely caused by a yeast infection and thus should not be treated with antibiotics.

As with almost all breastfeeding problems, a poor latch, and thus, poor draining of the breast sets up the situation where mastitis can occur.

Blocked Ducts

Blocked ducts will almost always resolve spontaneously within 24 to 48 hours after onset. During the time the block is present, the baby may be fussy when nursing on that side, as milk flow may be slower than usual. Blocked ducts can be made to resolve more quickly by:

  1. Continuing breastfeeding on the affected side.
  2. Draining the affected area better. One way of doing this is to position the baby so his chin "points" to the area of hardness. Thus, if the blocked duct is in the outside, lower area of your breast (about 4 o’clock), the football position would be best.
  3. Using breast compression while the baby is feeding (Handout #15 Breast Compression).
  4. Heat on the affected area (hot water bottle) also helps.
  5. The mother trying to rest. (Not always easy, but take the baby into bed with you).
  6. Sometimes a blocked duct is associated with a small blister on the end of the nipple. If you have this, you can open the blister with a sterile needle and squeezing out the toothpaste material in the duct (not always possible). This gives relief of nipple pain and may result in the blocked duct immediately resolving. Come to the clinic if you cannot open the blister yourself.

If a blocked duct has not settled within 48 hours (unusual), therapeutic ultrasound often works. This can be arranged at a neighbourhood physiotherapy office or sports medicine clinic. Many ultrasound therapists are not aware of this use of ultrasound. The dose of ultrasound is:

2 watts/cm2, continuous, for five minutes to the affected area, once daily for up to two doses.

If two treatments on two days do not work, there is no point in continuing with ultrasound. Get the blocked duct evaluated at the clinic or by your physician. Usually, however, if ultrasound is going to work, one treatment does the trick. Ultrasound also seems to prevent recurrent blocked duct which always occurs in the same place. Lecithin, one capsule (1200 mg) three or four times a day also seems to help prevent recurrent blocked ducts, at least for some mothers.

Mastitis: The following is my approach to dealing with mastitis.

If the mother has symptoms for more than 24 hours, she should start antibiotics. If the mother has symptoms for less than 24 hours, I will prescribe an antibiotic, but suggest the mother wait before starting the medicine. If, over the next 8-12 hours, her symptoms are worsening (more pain, spreading of the redness, enlargement of the hardened area), then the mother should start the antibiotics. If, 24 hours later, the mother has not worsened, but not improved, she should start the antibiotics. However, if symptoms are starting to decrease, there is no need to start the antibiotics. The symptoms usually continue to resolve and will have disappeared over the next 2 to 5 days. Fever will usually be gone within 24 hours, the pain within 24-48 hours, the breast hardness within the next couple of day. The redness may remain for a week or longer.

Once improvement begins, on or off antibiotics, it should continue. If you get worse, or symptoms do not continue to improve over 24 or 48 hours, call the clinic.


  • Continue breastfeeding, unless it is just too painful to do so. If you cannot continue breastfeeding, express your milk as best you can in the meantime, and restart breastfeeding as soon as you can. Continuing breastfeeding helps mastitis to resolve more rapidly. There is no danger to the baby.
  • Heat (hot water bottle) applied to the affected area helps fight off the infection.
  • Rest helps fight off infection.
  • Fever helps fight off infection. Treat fever if you feel bad, not just because you have it.
  • Take acetaminophen, ibuprofen or other medication for pain as you need it. You will feel better and there is no danger to the baby, who gets only a tiny amount.

Note: Amoxycillin, plain penicillin and other antibiotics are often ineffective for mastitis. If you need an antibiotic, you need one which is effective against Staphylococcus aureus. Effective for this bug are: cephalexin, cefaclor, cloxacillin, flucloxacillin, amoxycillin-clavulinic acid, clindamycin and ciprofloxacin. The last two are effective for mothers allergic to penicillin. You can and should continue breastfeeding with all these medications.

Abscess: Abscess occasionally complicates mastitis. You do not have to stop breastfeeding, not even on the affected side. Usually, the abscess needs to be drained surgically, but you should continue breastfeeding. Contact the clinic.

Handout #22. Blocked Ducts and Mastitis. Revised January 1998
Written by Jack Newman, MD, FRCPC
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Blocked Ducts and Mastitis