The Reason Why Your Nipples Get Hard
Nipples can be awkward, to say the least. First, there are the potential wardrobe malfunctions that can occur (well, at least if you're female and accidentally expose a nipple). Then there's the fact that nipples sometimes get hard with no warning and, depending on what you're wearing, might even be visibly erect through your shirt. What makes them do this? Why can't they just stay flat?
Nipples getting hard is a totally normal thing that happens to everyone, and it's nothing to be embarrassed about. One of the most common times nipples get hard is when you're cold. "In brief, nipples get hard for the same reason you get goose bumps on your skin," Dr. Michael Frederick told Teen Vogue. "We have very small smooth muscle cells in our skin and around our hair follicles that contract when it's cold to decrease the surface area of skin exposed to the cold. You will also notice that when your nipples get cold, the areola gets smaller at the same time because everything is getting tighter. This tightness then pushes out the nipple, and hence, cold weather gives you hard nipples."
That seems straightforward enough, but what about the other times that our nipples get hard? The nerves in your nipples react to physical and psychological stimuli, says Healthline. Some people have more sensitive nipples than others and will find that their nipples harden more easily. Things that can make your nipples harden include arousal, pregnancy, ovulation, breastfeeding, and even allergies. Nipples can even harden at random, and there's just no explanation for what's going on.
Most of the time, your nipples getting hard is a totally normal occurrence and nothing to worry about. If, however, the hardening is accompanied by pain or discharge, you should schedule a visit to your doctor to make sure that there isn't more going on.