Why Do Nipples Get Hard? The Science Behind The Phenomenon

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Why Do Nipples Get Hard? The Science Behind The Phenomenon

They get hard when we’re aroused and touched the right way. They also get hard when it’s cold, or when you just get out of the shower and the wind blows past you. They are sensitive, and everyone has ones that are slightly different from the next person.

Nipples, people. I’m talking about nipples

Why do nipples get hard?

Every human being is born with them, and yet they are so strange in so many ways. Perhaps the strangest thing about them is the fact that they tend to get hard from a variety of different stimuli. Most often, they harden up when they are exposed to cold, or when you’re sexually aroused.

Logically speaking, there’s not really an obvious reason as to why nipples would get hard.

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So, what gives? Believe it or not, scientists have been researching the answer to this question for quite some time.

Here’s what they found out.

The answer lies in the tissue and makeup of your nipples.

Nipples, like any other part of the human body, have nerve endings. These nerve endings are the very things that allow us to sense touch, or that tell our bodies to flex our muscles. Around our nipples, the nerve endings are ones that pick up on both physical and psychological stimuli.

So far, so normal, right?

Research has shown that the nerve endings present in our nipples are identical to the same nerve endings that give us the “hair standing on end” feeling. One scientist by the name of Alessando Furlan explained, "...One thing we found was that goosebumps and nipple erection are caused by neurons that are specialized to regulate these functions by controlling the erectile muscles in these tissues."

Many of the nerve endings found in nipples and the surrounding areas are from the sympathetic nervous system, the part of your nervous system that literally shows physical responses to emotional triggers

Things like having your hair stand on end from fear, having sweaty palms on a date, and even getting that “dry throat” feeling are all controlled by this part of the nervous system.

Surprisingly, our bodies have specialized nerve endings that tell our nipples to harden when confronted with certain stimuli. These nerve endings are part of our sympathetic nervous system, too.

The way our bodies are wired, our nipples naturally react to arousal by hardening. It’s an emotionally-triggered response, and it’s one that we can’t control any more than sweaty palms or blushing.

We’re not quite sure why this happens, but it’s possible that it has something to do with a woman’s ability to breastfeed children once they get pregnant.

When women breastfeed, nipples also end up hardening as a way to help babies latch on to the new supply of milk. Babies that are breastfed from nipples that can’t harden up often won’t be able to latch on as easily.

Though this is currently the biggest theory of the “why,” it’s important to point out that we still don’t know why the human body involves hardened nipples as a sign of arousal. Could it be a weird “crossed wires” thing?

Perhaps, but it could also be a way for our bodies to indicate that we’re turned on to our partners.

RELATED: The Real Reason Some People's Nipples Are So Sensitive

One thing to point out is that nipples also harden as a symptom of hormone-related issues in women.

There’s definitely a hormonal element to the mystery. Many women who are pregnant, menopausal, or even going through puberty tend to have nipples spontaneously become erect. The fluctuations that happen could be triggering a nervous response that science isn’t fully aware of yet.

So, what about the cold?

Oddly enough, the cold reaction isn’t fully understood by scientists, either. The current theory suggests that our nipples get erect due to hair follicles underneath and around the nipples’ surface.

When we’re cold, our hair stands on end as a way to trap warmth close to our skin. If this theory holds true, then the reason our nipples harden during the colder seasons is for the same reason. It’s a body’s way of trying to keep warmth inside rather than outside.

Moreover, areolas are a smooth muscle that is also wired to contract when stimulated through both temperature and touch. This can give a similar “hardened” appearance as well.

That being said, this trait seems to be one that no longer serves an evolutionary purpose. So, while it may have helped our ancestors in the past, there’s no sign that these traits are needed for anything other than causing embarrassing moments during winter.

Basically, we know the “how” behind the mystery, but not the “why.”

Right now, science doesn’t fully know the answer to the question "Why do nipples get hard?" especially during arousal, or what causes them to react to cold.

We do know a lot about the nervous system and how it plays into making our nipples get hard during times when there’s a lot of stimulation going on. However, the “why” of the question remains to be fully explained.

While we do have some pretty good running theories, we don’t entirely know why humans evolved this trait. That being said, it’s not a bad thing; it’s just another quirk of the human body.

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Ossiana Tepfenhart is a writer based out of Red Bank, New Jersey. She writes primarily about lifestyle, food, finance, and relationships. Follow her Twitter.