When we discuss body parts that grow, we don’t always contemplate the human nipple right away, but…let’s face it, they get hard. Remember that scene from Deuce Bigalow, American Gigolo? Yeah, we knew you would. You sicko! And although many of us can point out some occasions that are more likely to result in pointy nipples, how much do you really know about the biological or physiological processes at work?
Beverly Hills Plastic Surgeon Michelle Lee says, “Underneath the nipple and areola (the area surrounding the nipple), there are tiny muscles that contract and pull on the skin and push the nipple out.” When stimulated, “the sympathetic nervous system — part of the body’s neural wiring that makes your heart race, skin get goosebumps, and palms sweat — sends signals to the nerves in those tiny little muscles that cause them to contract.”
So it’s no surprise that these are often the situations that tend to result in hard nipples. Of course arousal can lead to stimulated and hard nipples, but any physical contact might be enough, especially since the nipples aren’t typically a part of the body that see a lot of action where touching is concerned.
Cold weather forces the same physiological reaction because those muscles want as much warm air as they can muster — and so they contract to keep more of it in. That’s basic science! Less surface area means less heat loss.
Another reason that your nipples might become erect? Hormones! Dr. Irobunda says, “During your period or even ovulation, changes in your hormone levels — especially estrogen — can cause your nipples to become harder.”
Dr. Lee adds, “During pregnancy, the hormone progesterone causes the formation of more milk lobules and duct systems. During breastfeeding, mechanical stimulation of the nipple from the baby causes the body to release oxytocin; this hormone acts on the milk glands to contract and push milk out to the baby.”