Few body parts provoke more intrigue than the nipple. Ostensibly nature’s mechanism for breastfeeding babies, the protrusions can be inverted, harbor sweat glands, and rarely come in matching pairs. Though they serve no apparent function in men, evolution hasn’t bothered knocking them out of the way. (Breast tissue develops before an embryo settles into a particular sex.)

Naturally, breastfeeding can induce some degree of discomfort or pain depending on a baby’s feeding frequency and their vampire-like voraciousness for nutrition. But why would a nipple hurt in the absence of a ravenous infant? A few reasons, and some might surprise you.

According to Medical News Today, the most common cause of sore nipples is friction. That doesn’t mean a mishap with a belt sander, either. For the sensitive nipple, chafing is often the result of exercising, with clothing like a shirt or ill-fitting bra making the area uncomfortable. The more your skin rubs up against the clothing, the more irritated it’ll get.

Runners even have a name for nipple pain while pounding pavement—jogger’s nipple. Long-distance runs and sweaty clothing conspire to cause pain or even bleeding. In the winter, erect nipples can be even more sensitive to the friction.

A hallmark of a friction-fried nipple is dry, flaking skin. If you find your chest is sore after a workout or a run, you may want to cover your nipples using a skin-friendly tape or Vaseline, or consider changing the kind of fabric you wear. Tighter clothing that won’t move over and around the nipple will also help. If you wear a bra, consider trying a different size. Already-damaged nipples can be washed and covered in a bandage until they heal.

Another common cause of nipple pain is an allergic reaction to laundry detergent. The same friction that can prompt discomfort during exercise can also be a problem for nipples if the fabric is prompting contact dermatitis, which is sometimes accompanied by a rash or redness. Laundry soaps can do this, as well as fabric softener. If your nipples have only recently developed sensitivity, see if it coincides with a change in your laundry habits. Opting for hypoallergenic products or 100 percent cotton might alleviate the issue.

If your nipples are continually irritated with broken skin present, it’s possible to develop a secondary bacterial or fungal infection, which can cause additional pain. Fungal infections might present as a bright pink nipple. In that instance, you’d want to see a doctor. Other causes of pain, like hormonal changes, are also best addressed by a medical professional. Keep in mind that nipple pain can be referred, meaning it can manifest even if other parts of the breast are having an issue. If discomfort persists, see your physician.

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