A red, swollen nipple is usually caused by irritation, infection, or a skin condition, and most cases resolve with straightforward treatment. But because a small number of causes are more serious, understanding what else is happening alongside the redness helps you figure out whether to wait it out or get it checked.
Friction and Contact Irritation
The simplest explanation is mechanical. Repetitive rubbing from clothing, especially during exercise, can leave nipples red, dry, irritated, and tender to the touch. Bleeding is possible in more severe cases. This is common enough among runners that it has a name: jogger’s nipple. Most cases feel better within a few days, though more severe chafing can take a few weeks to fully heal. Switching to softer fabrics, applying a barrier like petroleum jelly before activity, or using nipple covers typically prevents recurrence.
Chemical irritants are another frequent culprit. A preservative called isothiazolinone, commonly found in detergents, fabric softeners, and personal care products, can trigger contact dermatitis on the nipple and areola. In one study of patients with nipple eczema who tested positive for a specific allergen, 56% saw reduced flare-ups simply by avoiding products containing that ingredient. If your nipple redness coincides with a new soap, lotion, or laundry detergent, that’s a strong clue.
Nipple Eczema
Atopic dermatitis (eczema) can settle on the nipples just as it does on elbows or hands. It typically causes itching, flaking, redness, and mild swelling. One important detail: garden-variety eczema almost always affects both nipples. If you have a history of eczema or allergies elsewhere on your body, and both nipples are involved, a topical steroid cream from your doctor will usually bring relief within a couple of weeks. If it doesn’t improve in that time frame, further evaluation is warranted to rule out something else.
Infections: Mastitis and Thrush
Mastitis is an infection of the breast tissue that causes redness, swelling, warmth, tenderness, and often flu-like symptoms including fever and body aches. It’s most common during breastfeeding, when bacteria enter through a cracked nipple or a blocked milk duct, but it also happens outside of breastfeeding. The area may feel firm, and milk flow can decrease on the affected side. Antibiotics clear up most cases, and the sooner treatment starts, the less likely the infection is to progress.
Thrush, a yeast infection caused by Candida, looks different. The nipple and areola turn pink and may appear shiny, flaky, or cracked. The hallmark is pain that seems out of proportion to what you can see: a stabbing or shooting sensation deep in the breast during or after feeding, along with itching. Areola skin can become thickened and scaly. Thrush is most common in breastfeeding women and often follows a course of antibiotics, which can disrupt the normal balance of bacteria and yeast on the skin.
Periductal Mastitis and Smoking
A lesser-known cause of nipple redness and swelling is periductal mastitis, inflammation of the ducts just behind the nipple. It’s not related to breastfeeding and has a strong link to cigarette smoking. In a study comparing women with periductal mastitis to a control group, those with the condition were significantly more likely to smoke. Heavy smokers (more than ten cigarettes a day) had substantially more inflammation and tissue changes in the ducts than light smokers or nonsmokers. Cigarette smoke appears to have a direct toxic effect on the cells lining the milk ducts, triggering chronic inflammation that can lead to pain, redness, and discharge near the nipple.
If left untreated, periductal mastitis can progress to a subareolar abscess, a pocket of pus beneath the areola. Abscesses in non-breastfeeding women have a notably high recurrence rate, with some studies reporting recurrence in up to 50 to 57% of cases. Quitting smoking is one of the most effective ways to break the cycle.
Duct Ectasia
Mammary duct ectasia happens when the milk ducts beneath the nipple widen and their walls thicken, trapping a thick, sticky fluid. It’s most common in women between ages 45 and 55, during the transition to menopause. The discharge can be white, yellow, green, or black, and the nipple area may become red, tender, or swollen. Duct ectasia is benign and often resolves on its own, though the discharge can be persistent and frustrating.
When Redness Could Signal Cancer
Two rare but serious conditions can present as a red, swollen nipple, and knowing their distinctive features matters.
Inflammatory Breast Cancer
Inflammatory breast cancer is a fast-growing form in which cancer cells block the tiny lymph vessels in the skin of the breast. Rather than forming a lump, it causes the breast to turn pink, reddish-purple, or bruised-looking. The skin develops a dimpled, pitted texture resembling orange peel. The breast increases rapidly in size. These symptoms come on quickly, sometimes within weeks. Because it develops between routine screenings and doesn’t always show up on a mammogram, it’s often diagnosed at a later stage. Any rapid change in the size, color, or texture of one breast warrants prompt medical evaluation.
Paget’s Disease of the Nipple
Paget’s disease is a rare cancer that starts in the nipple itself. Early on, it can look almost identical to eczema: scaling, redness, and itching. The key differences are that Paget’s disease is almost always unilateral (one nipple only), progresses faster than eczema, and doesn’t respond to steroid creams. As it advances, the nipple may develop crusting, fissures, bloody or clear discharge, and eventually erosion or flattening of the nipple. If a topical steroid doesn’t improve nipple eczema within two weeks, current guidance recommends imaging and a biopsy, because even an MRI can sometimes miss biopsy-proven Paget’s disease.
How Doctors Evaluate a Red, Swollen Nipple
The workup depends on your age and symptoms. For women 30 and older, the standard first step is diagnostic mammography combined with ultrasound of the area behind the nipple. Ultrasound alone catches underlying problems in 56 to 80% of cases, which is better than mammography on its own, so the two are used together. For women under 30, ultrasound is typically the starting point, with mammography added if there’s a suspicious finding or a known genetic risk. For men 25 and older with nipple changes or discharge, mammography is also the recommended first imaging step.
If imaging looks normal but the skin changes persist, a biopsy of the affected skin is the definitive test. This is especially important for any one-sided nipple change that doesn’t heal, because both Paget’s disease and inflammatory breast cancer can be missed on imaging alone.
Practical Steps While You’re Figuring It Out
Start by ruling out the obvious. Switch to a fragrance-free detergent, skip fabric softener for a wash cycle, and wear a soft cotton bra or shirt for a few days. If you’re a runner or cyclist, protect the area with a barrier product. If you’re breastfeeding and have flu-like symptoms with breast redness, that pattern points strongly toward mastitis, and starting treatment quickly helps prevent abscess formation.
The features that should move you toward a medical visit sooner rather than later: redness limited to one side that doesn’t improve in one to two weeks, any pitting or orange-peel texture of the skin, rapid change in breast size, nipple inversion that’s new, bloody discharge, or a firm area beneath the nipple. Most causes of nipple redness are benign and highly treatable, but the serious ones share early symptoms with the harmless ones, which is exactly why persistent or one-sided changes deserve a closer look.