Different Types of Nipples: What You Need to Know

Nipples are as varied as breasts themselves. But broadly speaking, nipples can be categorized as either:

• Protruding (raised)
• Flat (flush with the skin)
• Inverted (sunken)
• Unclassified (various characteristics)

Nipples can differ in size, color, and texture. There are also uncommon variations like bifurcated nipples (two nipples next to each other), supernumerary nipples (an extra nipple elsewhere on the body), and athelia (missing nipples).

This article describes the four types of nipples a person can have, as well as common and uncommon variations in nipple structure and appearance.

Protruding Nipples

Roughly 75% of nipples are protruding. Still, their shape can vary from person to person. The average height of a nipple is 9 to 10 millimeters (roughly 1/3 of an inch).

For many people, protruding nipples are raised above the areola (the darker skin surrounding the nipple) all the time. The nipples can harden and stick out even further in response to cold, physical stimulation, or sexual arousal.

Flat Nipples

Flat nipples are the second most common type of nipple, occurring in roughly 23% of people. Some flat nipples will always remain flat, while others may become erect with cold temperatures, physical stimulation, or sexual arousal.

People with flat nipples may experience some difficulty with breastfeeding. Gently pulling the nipple forward and rolling it between the fingers can help engorge the tissues with blood, which can draw the nipple out enough for a baby to latch on more easily.

Using a breast pump or breast shells before breastfeeding or nipple shields while nursing can also help.

Inverted Nipples

Instead of protruding, inverted nipples are tucked below the skin's surface. As a result, they can appear dented or sucked in.

Inverted nipples can often protrude when gently stimulated. Some inverted nipples, however, will never protrude even with stimulation.

Nipple inversion is usually something someone is born with. Studies suggest that roughly 2% of nipples are this type.

Inverted nipples, also known as invaginated or retracted nipples, can result from shortened milk ducts that pull the nipple tissue inward. Although harmless, inverted nipples can make breastfeeding difficult.

Unclassified Nipples

Unclassified nipples are those that don't fit neatly into the above-listed categories. It can mean that there are unilateral (one-sided) variations in your nipples. For example, one nipple may be protruding and the other flat.

Variations like these may be due to a past injury or simply be something you were born with. However, they could also be a sign of a serious medical condition. Unilateral puckering, for instance, could be a sign of breast cancer.

Uncommon Variations

Nipple anomalies also fall under the category of unclassified nipples, These are almost always due to genetics and are rarely a cause of medical concern. Even so, some people may seek surgical correction for cosmetic reasons.

Uncommon nipple variations include:

• Supernumerary nipples: This is an extra nipple or nipples. Also known as polythelia, a supernumerary nipple can appear anywhere along the two parallel "milk lines" which start in each armpit, run through the "typical" nipple, and end at the groin.
• Bifurcated nipples: Also known as double nipples, this occurs when there are two nipples on one areola. The condition may be unilateral or bilateral (two-sided).
• Athelia: This is the absence of a nipple. In most cases, the condition is bilateral but can be unilateral if caused by genetic disorders such as Poland syndrome (in which a child is born with missing or underdeveloped chest muscles).

Other Nipple Variations

Beyond how raised or flat a nipple may be (or how many nipples you might have), there are other variations that characterize nipples.

Nipple Size

Nipple sizes can vary not only from person to person but also by biological sex. Due to evolutionary biology, female nipples are typically larger because they are functional and are needed to facilitate breastfeeding. They can also change in size under the influence of estrogen and progesterone.

In females, it is not uncommon for nipples to get bigger during periods or pregnancy. Both estrogen and progesterone draw fluid into the breasts, making nipples feel swollen and tender. In older males, the nipple and breasts may get larger due to a common aging-related condition called gynecomastia.

Studies suggest that female nipples are around 36% larger than nipples in males. While the size of nipples in males is relatively uniform, there can be a wide variation in size among females.

Nipple Color

The color of a nipple can vary by genetics and race, ranging from light pink to dark brown. The color usually matches that of the areola. Nipple color is not generally indicative of a health concern and can change with age or during menstruation, pregnancy, or menopause.

While suntanning can cause nipples to darken, other conditions can cause transient or permanent changes in nipple color.

One of these is hyperkeratosis, in which the outer layer of skin (stratum corneum) starts to thicken and harden, causing the skin to darken. Hyperkeratosis can occur for no known reason but can sometimes be the result of hormonal birth control or medications like spironolactone.

Nipple Texture

Nipples can also vary and change in texture. Tissue damage caused by breastfeeding, nipple piercing, or excessive sun exposure can cause nipples to become firmer, larger, dry, and flaky. By contrast, the aging-related loss of collagen can cause nipples to soften and sag.

It is also not uncommon to have pimple-like bumps on your nipples. These are due to glands called Montgomery tubercles located on the nipple and areola. During pregnancy, the glands can swell and turn milky white as they produce more oils to lubricate the nipple during breastfeeding.

Hairy Nipples

Hair follicles surround the nipples, so it's normal to have a few strands there. While the hairs may be thin and virtually transparent, with age, nipple hairs tend to become thicker and coarser.

In most cases, hairy nipples aren’t a cause for concern; they’re simply a part of the normal aging process. Plucking, tweezing, or shaving them can cause ingrown hairs and infection. Cutting the hair with nail scissors is a far better option.

When to See a Healthcare Provider

If you are born with flat or inverted nipples, they are not abnormal but are simply variations influenced by genetics. The same applies if your nipples change with age due to the loss of collagen and changes in hormones.

You should be concerned, however, if you experience sudden changes in your nipples, especially if you are younger, the changes are significant, or one nipple is affected but not the other.

Some examples of changes you should contact your healthcare provider about include:

• Nipple puckering: The one-sided inversion or puckering of a protruding or flat nipple should never be ignored. It may be due to duct ectasia (when milk ducts become swollen and clogged), but it could also be a sign of breast cancer (including Paget's disease of the nipple).
• Changes in texture or color: Scaly, flaky, or itchy nipples may be due to eczema or a fungal or bacterial infection. Redness, warmth, and pain may be a sign of an infection, the risk of which increases if nipples get dried or cracked.
• Swollen, enlarged pores: "Peau d'orange" is a term used to describe an orange-peel-like texture of skin that suddenly thickens and has enlarged pores. A nipple infection can cause this, but it is also a classic sign of inflammatory breast cancer.
• Excessive hair growth: The abnormal growth of hair around the nipples, called hirsutism, may be a sign of a hormonal disorder like polycystic ovary syndrome (PCOS) or Cushing's syndrome, as well as ovarian or testicular cancer.
• Abnormal discharge: Nipple discharge that is bloody, comes from only one nipple or comes out on its own without squeezing or touching the nipple may be a sign of an infection, benign growth on a milk duct, or breast cancer.
• Pain: Nipple pain may ache, tingle, throb, burn, or feel tender. While the cause of nipple pain usually isn't serious, in rare cases, it can be a sign of breast cancer. 

A benign condition called erosive adenomatosis of the nipple (EAN) is sometimes mistaken for Paget's disease of the nipple. EAN is characterized by:

• Erosion (sore or ulcer) on the nipple
• Clear fluid discharge
• Skin nodules
• Swelling
• Itching
• Erythema of the nipple (patchy redness and inflammation)

Although EAN is a benign condition, it should be examined by your healthcare provider to confirm the diagnosis.

How to Keep Your Nipples Healthy

These tips can help keep your nipples healthy:

• Wash your nipples with water only. Soaps and shower gels can remove the natural oils causing dryness and irritation.
• Air dry your nipples or pat gently with a towel (do not rub with a towel).
• Keep nipples dry.
• Change bras regularly to reduce the risk of fungal or bacterial infection.

Summary

Although most people have protruding nipples, they can vary in appearance. Flat and inverted nipples are variations that people are born with or that can develop due to aging. During puberty, pregnancy, and menopause, hormonal fluctuations can affect nipple appearance and sensitivity.

A few hair strands around the nipple are normal, but excessive hair growth can be caused by certain medical conditions. Notify your healthcare provider of any nipple changes, especially if they occur suddenly or only on one side.