Things to know about your nipple and areola skin and microbiome when you're lactating
Nipple and areola skin under the microscope
Skin is where our body ends and the rest of the world begins, a protective border at the edge of ourselves. Skin has its own secret intelligence, sorting out what elements of immune defence need to be secreted from its glands, what needs to be allowed to penetrate through, what needs to be kept out, what the skin needs to take into itself.
Most human skin has three variable layers, the epidermis, dermis, and the subcutaneous tissue. The subcutaneous base is a soft and sticky fatty layer, made up of loose connective tissue and fat lobules, which helps regulate body temperature and acts as a shock-absorber. But the nipple and areola complex, however, don’t have a subcutaneous layer.
Areola secretes a natural oil that is anti-bacterial and moistening. Trying to disinfect the nipple may cause damage and dermatitis, therefore paradoxically increasing the risk of infection. Avoid putting anything on the nipple (other than breast milk, and water in the shower) unless specifically prescribed.
The epidermis
The epidermis is a thin outer protective layer, which doesn’t contain sensory nerves or blood vessels. From an evolutionary perspective, keeping human tissues hydrated is fundamental to survival on land, so the outermost layer of the epidermis, the stratum corneum, is made up of multiple layers of flattened dead cells, which are impermeable and prevent water loss.
Under the stratum corneum, we find the cells known as keratinocytes, resting on the basal membrane. These keratinocytes are joined tightly to together by cell linkages. Keratinocytes produce many pro and anti-inflammatory chemical messengers, known as cytokines.
You may have noticed that the top surface of your nipple is covered with convoluted ridges. When I think about this from an evolutionary perspective, it seems to me that these corrugations have evolved to enhance epidermal elasticity when a woman is suckling her baby.
The dermis
The next layer down, the dermis, contains sensory nerve endings, including mechanoreceptors for the sense of touch or pressure, and nociceptors for the perception of pain. The dermis is a thick elastic fibrous structure, a complex network of collagen, which gives skin its mechanical strength. It's also highly vascular. Here, the pressure of fluid in the connective tissue controls the rate of lymphatic drainage.
There might be anywhere between none and forty areolar sebaceous glands embedded in the dermis of your areola, which open through little mounds onto the areola surface. These sebaceous glands secrete an anti-bacterial oil containing pheromones. The oil’s natural scent helps switch on baby’s breastfeeding reflexes. There are often sweat glands, too, and sometimes tiny little milk glands opening from the dermis to the nipple and areolar surface. This is why it’s best not to wipe or cleanse your breasts other than with water, nor to put anything other than your own breastmilk onto the nipples and areola before or after breastfeeding. Soaps, creams, lotions and other potions interfere with the cleansing and moisturising action of the sebaceous glands and may also cause moisture-associated skin damage, which we will discuss later.
The nipple and areola microbiome is part of your skin's immune system
Like skin on the rest of our body, healthy nipple and areola skin is a scaffold for microbial ecosystems known as microbiomes, including fungi, viruses, protozoa, and mites and more than a thousand species of bacteria. These bacteria are embedded in biofilm.
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Skin's microbiomes and biofilms extend deep into the layers beneath the epidermis, and participate in the body’s defence against environmental microbies which might cause disease. Before all else, the composition of skin microbiome is controlled by your body's immune system. But skin microbiomes are also shaped by your age, hormonal state, food and the place you live. Your skin microbiome with its biofilms is essential for skin health.
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The skin's immune system is a place of complex innumerable feedback loops. Biochemical signals, immune factors, and micro-organisms self-organise to keep this border between our bodies and the environment stable and protective.
It helps to know about the skin immune system, including skin microbiomes, when we consider nipple pain and wounds, and how best to heal.
You can find out about the special protections and also vulnerability of your nipple when you're breastfeeding here.
You can find out how your nipple skin adapts to breastfeeding here.
Recommended resources
The four main directions in which nipples look: what to do
What to notice in front of the mirror before you bring baby on to the breast
The protective powers of nipple and areolar skin when you're lactating
Things to know about your nipple and areola skin and microbiome when you're lactating
Your nipple skin knows how to adapt to the mechanical pressures of breastfeeding (or pumping)
The biological vulnerability of your nipple and areola skin when lactating