The epidermis is the outermost of three main skin layers. The outermost one is called the epidermis. It’s thin but durable and acts as a protective barrier between your body and the world around you.

The cells that make up the epidermis are continually being shed and replaced by new cells made in the lower levels of the epidermis.

The primary function of the epidermis is to protect your body by keeping things that might be harmful out and keeping the things your body needs to function properly in.

Bacteria, viruses and other infectious agents are kept out, helping prevent infections on your skin. Water and nutrients are kept in for the body to use. Body parts that are more susceptible to injury, like the soles of your feet and palms of your hands, have a thicker epidermis for even better protection.

Specialized cells in the epidermis help protect your body too:

Melanocytes

These cells contain a pigment called melanin and are responsible for your skin tone or color. Everyone has about the same number of melanocytes in their epidermis, but the amount of melanin in each cell differs among people. The more melanin you have, the darker your skin tone. Sunlight can increase the amount of melanin produced in melanocytes to a degree. This is what causes a suntan.

The other important role of melanocytes is filtering out ultraviolet (UV) radiation from the sun. UV radiation is the leading cause of skin cancer. It also causes wrinkles. People with darker skin have more melanin, so they can filter out more UV radiation and are less likely to get skin cancer and wrinkles.

Langerhans cells

These cells are part of your immune system. They act like guards and signal the body when they detect foreign substances, such as bacteria not usually found on your skin. This activates your immune system, which sends antibodies and other cells to fight an infection

The epidermis can be affected by several conditions and illnesses. Anything that irritates or injures your skin or sets off your immune system can negatively affect the epidermis. Infections can occur when bacteria get into the skin through a cut or other opening.

Some common conditions that affect the skin are:

Eczema

The different types of this condition all cause patches of itchy, inflamed, and reddened skin. It happens when something irritates your skin and your immune system reacts to it. According to the National Eczema Association, eczema affects over 30 million people in the United States.

Types of eczema
  • Atopic dermatitis is a chronic, severe form of eczema that’s triggered by an allergic reaction and often causes open sores that weep or are crusty in addition to the typical eczema symptoms.
  • Contact dermatitis is triggered by specific things your skin comes in contact with, such as a certain brand of laundry detergent or make-up and may cause a burning sensation.
  • Dyshidrotic eczema can be triggered by stress or moisture on your hands, and causes blisters and itchy inflamed skin on the sides of your palms and fingers of your hands or your toes and soles of your feet.
  • Seborrheic dermatitis, like dandruff, is due to unknown triggers, and it produces patches of red greasy skin with a white crust that flakes off.

Erysipelas

This is an infection of the epidermis, but it can extend down into the skin layer below the epidermis, called the dermis. The affected skin is salmon-colored with well-defined edges that stick up above the skin surface.

Impetigo

This is a contagious infection that affects only the uppermost part of the epidermis. It occurs most often in babies and small children. The infected skin is red with pus-filled blisters that break open and crust over.

Psoriasis

In this condition, your immune system inappropriately attacks your skin, causing rapid growth of skin cells. All the skin cells pile up and form a silvery, scaly area, called a plaque. The skin becomes very itchy and can be painful.

Skin cancer

There are three types of skin cancer:

  • Basal cell carcinoma. The most common type of skin cancer, over four million Americans are diagnosed with it every year according to The Skin Cancer Foundation. In starts in the deepest part of the epidermis, and it rarely spreads (metastasizes) to other body parts. It isn’t usually found on areas exposed to the sun, but it is caused by UV radiation from the sun.
  • Squamous cell carcinoma. This type of skin cancer can metastasize if not treated in time, and it grows rapidly. It’s usually found on areas exposed to the sun like bald heads, cheeks, and noses.
  • Malignant melanoma. This type of skin cancer starts in melanocytes. It can metastasize all over the body if not treated early. Most often it starts as a new mole, but sometimes it grows from a mole that has been there for a long time.

Many skin conditions start in structures in the layer below the epidermis, called the dermis, but expand up into the epidermis. Some of these conditions are:

Acne

According to the American Academy of Dermatology, in the United States, acne is the most frequently seen skin problem. Acne forms when the small openings in your skin, called pores, get blocked by the buildup of dead skin, dirt, bacteria and oil.

Cellulitis

This infection can be seen in the epidermis and on the skin surface, but it spreads downward into the subcutaneous fat layer and other tissues underneath the skin, such as the muscle. It can make you very sick and cause other symptoms like fever and chills. The skin rash is usually blistered and very painful.

Sebaceous cyst

This usually develops when the opening of a sebaceous gland becomes blocked and the gland fills up with a thick liquid. They are harmless, and small cysts usually have no symptoms. When they get very large, they can be painful.

It’s important to keep the outer layer of your skin healthy so it can do its job of protecting your body. When an area of your skin gets a cut or sore or breaks down, bacteria and other harmful substances can get into your body and make you sick.

Tips for Healthy Skin
  • Washing regularly. This gets rid of oil, dead skin cells, and bacteria that can block pores or contribute to skin break down
  • Clean off sweat. Wash after activities that make you sweat, like sports or being in the heat.
  • Use mild soap. Harsh products may be full of chemicals that irritate your skin. Shop for mild soap.

Underneath the epidermis, there are two more layers in your skin.

Dermal layer

This is the layer underneath the epidermis. It is much thicker and sturdier than the epidermis. It contains elastin, which makes your skin flexible, so it returns to its original shape after it’s moved or stretched. The dermis contains several important structures:

  • Sweat glands.These produce sweat that helps your body stay cool when it evaporates from your skin. It’s also a way for your body to remove some of its waste products.
  • Hair follicles.Hair is produced in these tubular structures. Each follicle contains a small muscle that causes you to have goose bumps when it contracts.
  • Oil (sebaceous) glands.Connected to the hair follicle, these glands produce an oily substance, called sebum, that keeps your skin and hair lubricated. It also helps protect your skin and helps make it water resistant.
  • Nerve endings.These allow your skin to feel things.
  • Blood vessels. These bring blood to your skin and move waste products, like carbon dioxide, away from your skin.

Subcutaneous fat layer

This layer of fatty tissue helps keep your body from getting too hot or too cold. It adds padding to your body to protect the bones and tissues when you fall, get hit, or bump into things. It’s also a storage space for energy that your body can use when it needs it. The thickness of this skin layer varies depending on the area of the body and based on your weight.

The epidermis is the outer layer of your skin, and it plays an important role in protecting your body from things like infection, UV radiation, and losing important nutrients and water. Taking care of your epidermis by keeping it clean, avoiding harsh chemicals, and staying out of the sun will help ensure that it stays healthy and continues its job of protecting your body for a very long time.