Skin: The Human Body's Largest Organ (2023)

By Kim Ann Zimmermann


Skin: The Human Body's Largest Organ (1)

Skin is more than a fleshy surface for pimples, tattoos and wrinkles. Skin is the body's largest organ, and along with hair, nails, glands and nerves, is part of the integumentary system, according to Oregon State University. This system acts as a protective barrier between the outside and the inside of the body.

In adults, skin accounts for about16 percent oftotal body weightand covers a surface area of approximately 22 square feet (2 square meters).

There are different thicknesses and textures of skin on different parts of the body. For example, skin is paper-thin underneath the eyes, but is thick on the soles of the feet and palms of the hand, according to the Johns Hopkins Medicine Health Library.

Three layers of tissue

Human skin is composed of three layers of tissue: the epidermis, dermis and hypodermis, according to the Cleveland Clinic.


The epidermis is the top, visible layer of skin and it's constantly being renewed as dead skin cells are shedon a daily basis. The main functions of the epidermis include:

  • Making new skin cells. New skin cells form at the bottom of the epidermis. As these newer cells form, it takes them about one month to reach the top layer of the epidermis. The new cells will replace the old cellsfound on the skin surface, which are dead and continuously flake off.
  • Giving skin its color. The epidermis contains melanocytes, which are cells that produce melanin, the pigment that gives skin its color. Melanin is also responsible for suntans and freckles.
  • Protecting skin. Keratin, a protein made by cells found in the epidermis, gives skin its toughness and strength, and protects skin from drying out.


The dermis is the middle layer of skin, found underneath the epidermis. It is the thickest layer of skin and contains nerves and blood vessels. It is also home to the sweat glands, oil glands and hair follicles. The dermis gives skin its flexibility and strength, according to the Johns Hopkins Medicine Health Library. It is made up mostly of a protein called collagen that makes skin stretchy and strong.

According to the National Library of Medicine, the roles of the dermis include:

  • Sensing pain and touch. Nerve endings in the dermis contain receptors that transmit sensations, such as pain, pressure, touch, itchiness and temperature to the brain.
  • Producing sweat and oils. Sweat glands help to cool the body, and sebaceous glands make the oils that keep skin soft and moist.
  • Growing hair. Hair follicles found in the dermis grow the hair on your head, face and body. That hair also helps to control body temperature and protect the body from injury.
  • Bringing blood to the skin. Blood vesselsfound in the dermis nourish the skin and help control body temperature. When skin becomes too hot, blood vessels enlarge to release heat from the skin's surface, while cold constricts blood vessels so they retain body heat.
  • Fighting infection. Lymphatic vessels, which drain fluid from the tissues and are an important part of the immune system, are housed in the dermis. They help ward off infections and other harmful substances.


The hypodermis — also called subcutaneous fat — is the deepest layer of skin. This layer is made up mostly of fatty tissue, which helps to insulate the body from heat and cold. The hypodermis also serves as an energy storage area for fat. This fat provides padding to cushion internal organs as well as muscle and bones, and protects the body from injuries, according to the Johns Hopkins Medicine Health Library.

Common skin conditions

Dermatologists are physicians who specialize in treating diseases, disorders and injuries of the skin, hair and nails. They treat common conditions such as acne and warts; chronic skin conditions such as eczema and psoriasis;and more serious diseases like skin cancer, according to the American Academy of Dermatology(AAD).

Warts and moles

Warts are benign(noncancerous) growths on the skin caused by the human papillomavirus (HPV), according to the AAD. They often occur on the hands and soles. Sometimes, tiny black dots will be visible in a wart.

"These are blocked blood vessels, which are a common occurrence with a papilloma viral infection," said Dr. Charles E. Crutchfield, a clinical professor of dermatology at theUniversity of Minnesota Medical School, and medical director ofCrutchfield Dermatology.

The best treatment for wartsis to cause a mild irritation of these skin growths — usually by freezing them, applying a chemical such as salicylic acid or using lasers — so the immune system can recognize the viral infection and get rid of it.

Moles are another type of common growth on the skin. They're most often brown or black, but some can be red or skin-colored, and they may appear flat or raised. If a mole starts changing in size, color or shape, or if it bleeds and doesn't heal on its own in three weeks, it should be evaluated to make sure it's not turning into skin cancer, Crutchfield said.

Acne and eczema

Acne, a disorder of the hair and oil glands, is among the most common skin conditions treated by dermatologists, Crutchfield told Live Science.

Acne occurs when hair follicles become plugged with oil and dead skin cells, according to the Mayo Clinic. The condition presents itself as red bumps and pimples on the face, chest and back, Crutchfield said. Treatments for acne include vitamin A products (retinols prevent plugging of hair follicles), salicylic acid (to unplug pores), benzoyl peroxides (to decrease bacteria) and antibiotics (to reduce inflammation).

Eczemalooks like patches of red, itchy, bumpy skin, and the most common type is known as atopic dermatitis. The condition can occur anywhere on the skin. Sometimes, it flares up on its own, and at other times, it is caused by a specific trigger, such as a skin irritant likepoison ivy, or exposure to an allergen, according to Crutchfield.

Eczema is best treated with topical anti-inflammatory creams and ointments, which can reduce itching and redness. For mild symptoms, over-the-counter medications work well, but a prescription-strength cortisone product may be needed for more severe cases.

Skin cancer

Skin canceris an abnormal growth of skin cells, and the most common type is basal cell carcinoma, Crutchfield said. More than 4 million cases of basal cell carcinoma are diagnosed in the United States each year, according to the Skin Cancer Foundation. This type of cancer is skin colored, pink or has a slight pearly white color to it, and usually appears on sun-exposed areas of the face, ears or neck, according to the Mayo Clinic. It rarely spreads to other parts of the body, but it can be very problematicif it's not treated, Crutchfield cautioned.

The second most common type of skin cancer is squamous cell carcinoma. It may appear as a pink or white bump, a rough, scaly patch or a sore that won't heal, according to the AAD.

The most serious skin cancer is melanoma, which looks like a dark, changing, bleeding skin spot, Crutchfield said. This cancer begins in the skin's pigment-producing cells, and although it is the rarest form of skin cancer, it causes the majority of skin cancer deaths.

Additional resources:

This article was updated on Oct. 22, 2018 by Live Science Contributor, Cari Nierenberg.

Kim Ann Zimmermann

Live Science Contributor

Kim Ann Zimmermann is a contributor to Live Science. She holds a bachelor’s degree in communications from Glassboro State College.


Why skin is the largest organ of the body? ›

To date, the skin is considered to be the largest organ. It covers your whole body and makes up about 16 percent of your overall body mass. Your skin is approximately 2 millimeters thick.

Is the skin the second largest organ? ›

Skin is the human body's largest organ. Body organs aren't all internal like the brain or the heart. There's one we wear on the outside. Skin is our largest organ—adults carry some 8 pounds (3.6 kilograms) and 22 square feet (2 square meters) of it.

Why is the skin important to the body? ›

Your skin is the organ that comes into contact with the rest of the world. It holds body fluids in, preventing dehydration (dee-hahy-DREY-shun), and keeps harmful microbes (MYE-krobs) out—without it, we would get infections. Your skin is full of nerve endings that help you feel things like heat, cold, and pain.

Why is the skin considered an organ? ›

The skin is an organ because it is composed of tissues working together. The main three tissues are: The epidermis, the outermost layer of skin. The dermis, under the epidermis.

Can a person survive without skin? ›

You couldn't live without the skin you're in. Find out what's going on under the surface in the skin video.

What are some fun facts about skin? ›

Your skin makes up about 15% of your total body weight. The average adult has nearly 21 square feet of skin that contains over 11 miles of blood vessels. A single square inch of skin has about 300 sweat glands. The thickest skin is found on your feet and the thinnest area of skin are your eyelids.

What is the 2 largest organ in the body? ›

Did you know that your liver is the second largest? That makes it the largest solid internal organ you have, weighing in at 3-3.5 pounds. It is located underneath your ribs, lungs, and diaphragm, and on top of your gallbladder, stomach, and intestines.

What are the 5 main organs? ›

The human body contains five organs that are considered vital for survival. They are the heart, brain, kidneys, liver, and lungs. The locations of these five organs and several other internal organs are shown in Figure 10.4.

What are the 10 largest organs of the body? ›

The ten largest organs in the body are – skin, liver, brain, lungs, heart, kidney, spleen, pancreas, thyroid and joints. Let us discover interesting information related to the main largest organs in the human body.

How often does your skin replace itself? ›

Throughout your life, your skin will change constantly, for better or worse. In fact, your skin will regenerate itself approximately every 27 days. Proper skin care is essential to maintaining the health and vitality of this protective organ.

Why does skin protect us? ›

It protects the body from external factors such as bacteria, chemicals, and temperature. The skin contains secretions that can kill bacteria and the pigment melanin provides a chemical pigment defense against ultraviolet light that can damage skin cells.

What keeps your skin healthy? ›

Eat a healthy diet

Eat plenty of fruits, vegetables, whole grains and lean proteins. The association between diet and acne isn't clear — but some research suggests that a diet rich in fish oil or fish oil supplements and low in unhealthy fats and processed or refined carbohydrates might promote younger looking skin.

What are 4 functions of the skin? ›

Provides a protective barrier against mechanical, thermal and physical injury and hazardous substances. Prevents loss of moisture. Reduces harmful effects of UV radiation. Acts as a sensory organ (touch, detects temperature).

What is your skin made of? ›

What is the skin? The skin is the body's largest organ, made of water, protein, fats and minerals. Your skin protects your body from germs and regulates body temperature. Nerves in the skin help you feel sensations like hot and cold.

What is the smallest organ? ›

Pineal gland:
  • The smallest organ is the pineal gland.
  • It is situated centrally in the brain.
  • It is the main site for the secretion of melatonin that controls the internal clock of the body.

How long can a human live skinned? ›

Dermatologist Ernst G. Jung notes that the typical causes of death due to flaying are shock, critical loss of blood or other body fluids, hypothermia, or infections, and that the actual death is estimated to occur from a few hours up to a few days after the flaying.

What can dead skin do? ›

If these extra cells aren't removed, either on their own or by us, the buildup can make our skin look dehydrated and dull. Dead skin cells can also clog our pores or hair follicles, which is why they can cause acne breakouts, especially for people who already have acne prone skin.

Is human skin waterproof? ›

Skin is a waterproof, flexible, but tough protective covering for your body. Normally the surface is smooth, punctuated only with hair and pores for sweat. A cross-section of skin shows the major parts. It is divided into three layers.

Where is skin the thickest? ›

Epidermis varies in thickness throughout the body depending mainly on frictional forces and is thickest on the palms of the hands and soles of the feet, and thinnest in the face (eyelids) and genitalia.

What skin says about your health? ›

Color changes to the skin can sometimes indicate underlying illness. "Skin sometimes looks gray, sallower, in people with underlying chronic illness," says Dr. Brod. Yellowish- or orangish-looking skin can be a sign of kidney or liver disease.

What organ is heaviest? ›

The following are the six heaviest organs found in the body of a human being:
  • The first heaviest organ is the skin with a mass of four to five kg.
  • The liver is the second heaviest organ in the body, which discharges bile. ...
  • The brain is the third heaviest organ with an approximate mass of 1.5 kg.

What are the 7 vital organs? ›

Scientific view
  • The brain. The brain is the control centre of the nervous system and is located within the skull. ...
  • The lungs. The lungs are two sponge-like, cone-shaped structures that fill most of the chest cavity. ...
  • The liver. ...
  • The bladder. ...
  • The kidneys. ...
  • The heart. ...
  • The stomach. ...
  • The intestines.
Nov 14, 2018

Which organs hold emotions? ›

Organs and Emotions
HeartOver Joy/ Anxiety
Mar 7, 2016

What is the largest and most important organ of the body? ›

The brain is arguably the most important organ in the human body. It controls and coordinates actions and reactions, allows us to think and feel, and enables us to have memories and feelings—all the things that make us human.

What is the largest organ in the world? ›

Fact: Boardwalk Hall also houses an enormous musical treasure: the Midmer-Losh Pipe Organ, which was then and is still today the biggest organ in the world.

Is skin the largest organ on every animal? ›

The skin is the largest organ of the body and, depending on the species and age, may represent 12%–24% of an animal's body weight.

What is the least important organ? ›

The appendix may be the most commonly known useless organ.

While plant-eating vertebrates still rely on their appendix to help process plants, the organ is not part of the human digestive system.

What is the 4 largest organ in the body? ›

Healthline reports that the top five largest organs in the human body are:
  • Skin.
  • Liver.
  • Lungs.
  • Heart.
  • Kidneys.
Sep 24, 2022

What is the new largest organ? ›

Researchers also suggested that the newly discovered organ, called the interstitium, might be the largest organ in the body. That's right: The skin, long touted as the body's largest organ in middle-school science classes across the country, would lose its No.

What are the top 10 biggest organs? ›

The ten largest organs in the body are – skin, liver, brain, lungs, heart, kidney, spleen, pancreas, thyroid and joints. Let us discover interesting information related to the main largest organs in the human body.


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