Why your nipples get hard when it’s cold, the truth about boob orgasms and 9 other bizarre breast facts

FEW body parts are talked about as often as breasts.

We have a myriad of nicknames and slang terms for them, we talk about whether to breastfeed or not, discuss their size, shape and much more.

But even if you have breasts, certain aspects of them may still remain a mystery to you.

For example, have you ever wondered why your nipples get hard when you're cold? Or whether it's normal that one boob seems a cup size larger than the other?

From 'nipple orgasms' to whether size matters when it comes to breastfeeding and how babies can produce milk too, here are some weird and wonderful facts about breasts that you might not be aware of.

1. You don't have control over nipple erections

Your nipples are full of nerve endings which respond to stimulation, which can include touch and changes in temperature. 

One of the body’s responses to cold is to get goosebumps as the smooth muscle under the skin contracts to trap warm air near the skin. 

Smooth muscle is not under your voluntary control.

You don’t think about it, just as you don’t think about contracting the muscles in your intestines, they just keep moving.

There is smooth muscle under your areole that contracts as you become cold, pulling the skin and making the nipple erect. 

Any form of touch, sexual or not, even your clothes brushing against the nipple, can cause a similar response.

2. No other primate has permanent breasts

Only humans have permanent breasts.

In primates the breasts grow during pregnancy and breastfeeding and then shrink down again.

It is only humans who grow breasts at puberty and then keep them throughout life, though they change with time. 

There are lots of theories as to why this is, including breasts being something for a baby to hold onto after feeding!

3. You can have nipple orgasms

Nipples have multiple purposes, from delivering breast milk to providing sexual arousal and satisfaction. 

In all genders, the nipples are an erogenous zone, stimulating the nipples can even lead to ‘nipple orgasm’, where you can reach an orgasm solely by stimulating the nipples alone, without touching the genitals.

This is because stimulating the nipples releases the hormone oxytocin, which is involved in orgasm and triggers brain activity in the same area of the brain as when the genitals are stimulated!

4. One breast can be a cup size larger than the other

There's a reason breasts are often referred to as sisters, not twins.

Breasts are not exactly the same shape and size and it is normal for there to be some asymmetry between them.

It is likely that they are different sizes, up to about a cup size in difference.

5. Babies can produce breast milk

The majority of newborn babies - around 65 to 90 per cent - will actually have some breast tissue at birth, called breast buds.

This is due to the transfer of hormones from the mother during pregnancy and tends to go away on their own within a few weeks of birth. 

These hormone changes can stimulate the production of a clear or milky coloured fluid from the nipple, sometimes called witch’s milk which also goes away on its own.

6. Nipples develop before genitals in the womb

This is why males have nipples.

Both breasts and nipples are already starting to develop extremely early in pregnancy, at about four to six weeks. 

The Y chromosome in males means that the testes begin to develop at around seven to nine weeks of pregnancy, and by this point the nipples are already there in all genders.

Having extra or accessory nipples is actually relatively common, occurring in about one to five out of every 100 people.

These can range in size and may be so small you may think they are a scar, for example from chickenpox.

They tend to occur along the ‘milk line’ – an imaginary line from your armpits to your groin which is where breast tissue develops in the womb. 

You can also get extra/accessory breasts, which may be present from birth or you might only notice them after puberty. 

Having extra nipples or breast tissue is not a medical cause for concern but don’t forget to examine them when you are checking yourself.

7. Breasts don’t contain muscle

The breasts don’t actually contain any muscle, they are made up of the milk producing glands and ducts and fatty tissue along with some ligaments and connective tissue for support and shape. 

The skin of the breasts also has a role in supporting the breasts. 

But the breasts do sit on top of your pectoral muscles, exercising these doesn’t increase the size of the breast but may affect their appearance.

8. Breasts change every month

During the reproductive years, your breasts change each and every menstrual cycle, getting ready for a potential pregnancy and breastfeeding whether or not you are even trying to get pregnant!

Breast tissue responds to the hormones of the menstrual cycle, with oestrogen stimulating the growth of milk ducts in the breast and progesterone stimulating the formation of milk glands and breast lobules.

These hormonal changes and breast changes can lead to symptoms such as breast tenderness and discomfort, called cylical mastalgia.

9. Breasts move

Breasts move, a lot.

In fact they don’t just move up and down during exercise and physical activity but in all directions, up down, in and out and sideways.

Walking can result in breast movement of about four centimetres and during running there can be movement of about 12-15cm, even up to around 20cm during jumping jacks!

Wearing a well fitting, supportive sports bra can be helpful to prevent this movement and therefore pain.

This is hugely important as in one study almost one in five women reported that their breasts are a barrier to exercise, with all its physical and mental health benefits. 

10. Size doesn’t matter when it comes to breastfeeding

The production of breast milk is not dependent on the size of your breasts, you can produce breast milk irrespective of your breast size. 

But, different breasts will store different amounts of milk, and this is also unrelated to size.

If your breasts are able to store a lot of milk you can deliver more at one feed and may be able to go longer between feeds, while if they store less you may need to feed more frequently. 

You may even notice that each of your breasts can store a different amount of milk.

Remember, storage is not the same as production - whether or not  you store a lot or a little you will be able to produce milk,  you just might have to feed more frequently.

Milk is produced continuously, you don’t need to drain the breast and then wait for it to fill up, the more milk that is drained, the more will be produced.

On average babies drink about two thirds of the available milk at each feed.

11. Breast milk changes throughout the day

Breast milk is made of carbohydrates, fats, protein and more and the exact composition will vary, not just between people, but also within the same person at different times of the day to meet the needs of the baby.

Milk produced at night contains higher levels of the amino acid tryptophan which makes you feel relaxed and sleepy.

There are also different types of milk within breastmilk, the foremilk which is released first is more watery and the hindmilk, which comes after is higher in fat content.

Breast milk is naturally creamy and sweet and the taste can even be affected by the food that you eat.

It may even have an influence on your baby’s taste preferences later on.