Human skin can have a large number of different colors, some of which indicate an abnormality. Common examples of this are jaundice, bruising and redness from sunburn. Intake of certain nutrients can lead to discoloration of the skin. The color based on the amount of pigment can vary from light pink to almost black. In particular, people with ancestors from sunny regions (such as near the equator) often have a darker skin color than people with ancestors where the sun shines less brightly. Dark skin can be a great advantage due to the production of melanin, a substance that protects the skin against the harmful effects of the sun.
Table of contents
- Anatomy and function of the skin
- Jaundice
- Carotenemia
- Cyanosis
- Anemia
- Erythema
- Algyria
- Pigment related disorders
Anatomy and function of the skin
Function
In medicine, the skin is considered a separate organ, just like the heart and lungs. A specialist in the field of the skin is called a dermatologist. The skin is the heaviest organ and weighs approximately 16% of the total body weight, at 70kg this is approximately 11 kilos. This also includes so-called skin appendages, consisting of nails, hair and sebaceous and sweat glands. The skin is thinnest under the eyelids, approximately 0.5 mm, and thickest under the soles of the feet, at approximately 4 mm. Key features include:
- Preventing dehydration: By forming a layer between the internal and external environment. The skin is water resistant, so no water is lost.
- Insulation
- Temperature regulation: Through venous dilation and sweat glands, the skin can help cool or warm the body
- Sensibility (feeling): Through nerve endings the skin plays an important role in the perception of heat, cold, movement and vibration
- Production of vitamin D
Overview of layers of epidermis / Source: Public domain, Wikimedia Commons (PD)
Anatomy
The skin consists of two layers, namely the dermis and the epidermis. Below this lies the subcutis, which consists mainly of fat. The epidermis is the most superficial layer of the skin and is divided into five sublayers, from superficial to deep respectively:
- Stratum corneum (stratum corneum): Mainly dead skin cells, water resistant
- Stratum lucidum: This is so called because it is a clear layer under the microscope. This is only present on the palm and soles of the feet
- Stratum granulosum: This layer contains the so-called keratohyaline granules
- Stratum spinosum (spine cell layer)
- Stratum basale: This is the layer with the most living cells, from here they increasingly reach the surface. This layer contains the so-called melanocytes, the pigment (melanin) producing cells. Melanin has a protective effect against the harmful effects of sunlight. The condition in which no melanin is produced is called albinism. These people have a clearly increased risk of developing skin cancer.
The dermis: The skin owes its firmness to this, it consists mainly of connective tissue. This is also where the blood vessels, nerves, hair roots and sebaceous/sweat glands are located.
Jaundice in man with liver dysfunction / Source: James Heilman, MD, Wikimedia Commons (CC BY-3.0)
Jaundice
Jaundice (Icterus) is a yellow discoloration of the skin and sclerae (whites of the eyes). This indicates an increased concentration of bilirubin in the skin and usually also in the blood, which becomes visible from a level of >50µmol/L. Bilirubin is a breakdown product of hemoglobin, a substance found in red blood cells to which oxygen binds. The substance is processed by the liver. The breakdown of bilirubin is promoted by ultraviolet light, which is why babies with jaundice are exposed to the sun or artificial light. Possible causes of jaundice may include:
- An excessive supply of hemoglobin (for example because red blood cells have a short lifespan) and, for example, because the liver cannot get rid of the processed bilirubin.
- Reduced function of the liver (for example due to liver inflammation: hepatitis, or in newborn babies where the liver does not yet function optimally)
- A disorder in the flow of bilirubin through the liver, such as a blockage of the draining bile ducts by a gallstone or a pancreatic tumor
Child with carotenemia, especially of the nose / Source: Foiltape, Wikimedia Commons (CC BY-3.0)
Carotenemia
Carotenemia causes an orange discoloration of the skin, usually due to excessive intake of food containing carotene (provitamin A). It can be distinguished from jaundice because it does not discolor the mucous membranes of the skin (including the cornea). The supply of carotene exceeds the body’s ability to break down this substance, resulting in an accumulation. It takes about 1-2 months after a diet change to develop. Carotene is mainly found in orange-colored fruits and vegetables such as mangoes, carrots and mandarins. It is also present in green leafy vegetables, such as spinach and cabbage. Another cause of the skin turning orange is a number of chronic conditions.
Peripheral cyanosis of the hand / Source: James Heilman, MD, Wikimedia Commons (CC BY-SA-3.0)
Cyanosis
Cyanosis can be a cause of a blue discoloration of the skin. It is a result of a reduced amount of oxygen bound to the red blood cells. It occurs when more than 2 g/dL of hemoglobin has no longer bound an oxygen molecule. It may indicate a serious and acute lack of oxygen and therefore be a reason to contact a doctor. A distinction is made between peripheral (of the hands and feet) and a central form.
Anemia
Pale skin can be caused by several conditions, including anemia, low blood pressure and relatively lower levels of melanin due to reduced sun exposure (hypopigmentation). Anemia can have a wide variety of symptoms. In the case of severely reduced blood pressure, such as shock due to blood loss, the body will send most of the blood to the vital organs (heart, lungs, brain) and the skin will receive less blood. This makes the skin less red.
Erythema
A red discoloration of the skin (erythema) indicates an increase in blood flow to the skin. The response to inflammation due to damage to the skin with, for example, a chemical substance, an allergic reaction to a bee sting, sun rays or certain types of medicines.
Agyria in 92 year old man / Source: Herbert L. Fred, MD and Hendrik A. van Dijk, Wikimedia Commons (CC BY-2.0)
Algyria
Argyria is a very rare condition in which the skin and mucous membranes show a blue/gray discoloration due to increased exposure to silver. It is a condition that can be caused by long-term silver intake, which accumulates in the body. There is no known convincing treatment, the consequences for the body are limited.
Vitiligo in dark skin / Source: James Heilman, Wikimedia Commons (CC BY-SA-3.0)
Pigment related disorders
Vitiligo
This condition involves the complete absence of pigment-producing cells in certain regions of the skin and hair. This results in complete discoloration. It occurs in about 1 in 200 people. The exact cause is still unknown, but hereditary factors play an important role. It may be an autoimmune disorder. The disease is not contagious.
Example of melanoma / Source: National Cancer Institute, Wikimedia Commons (Public domain)
Melanoma
A melanoma is a serious form of a skin tumor that arises from melanocytes. One should be particularly concerned about new or changing moles and it is advisable to contact a GP if you are concerned. The same applies to moles that suddenly start to hurt, bleed or itch. Risk factors for melanoma include high sun exposure and a light skin type. review
