With mastitis, signs and symptoms can appear suddenly and may include:
- Breast tenderness or warmth to the touch
- Generally feeling ill (malaise)
- Swelling of the breast
- Pain or a burning sensation continuously or while breast-feeding
- Skin redness, often in a wedge-shaped pattern
- Fever of 101 F (38.3 C) or greater
Although mastitis usually occurs in the first several weeks of breast-feeding, it can happen anytime during breast-feeding. Lactation mastitis tends to affect only one breast — not both breasts.
When to see a doctor
In most cases, you'll feel ill with flu-like symptoms for several hours before you recognize that there's a sore red area on one of your breasts. As soon as you recognize this combination of signs and symptoms, it's time to contact your doctor.
Your doctor will probably want to see you to confirm the diagnosis. Oral antibiotics are usually very effective in treating this condition. If you've had mastitis before, your doctor may prescribe antibiotics over the phone. If your signs and symptoms don't improve after the first two days of taking antibiotics, see your doctor right away to make sure your condition isn't the result of a more serious problem.
Source: http://www.mayoclinic.com