Diseases, Injuries, and Disorders of the Integumentary System

Burns

A burn is a type of injury to flesh caused by heat, electricity, chemicals, light, radiation, or friction.

Learning Objectives

Classify burns by depth of injury

Key Takeaways

Key Points

  • Most burns affect only the first two layers of the skin, the epidermis and dermis.
  • Burns are classified by severity, surface area involvement, and depth of injury.
  • Burns are also classified as major or minor depending on a combination of factors including age, thickness of burns, surface area of the body involved, and the presence of inhalation injury.
  • First degree burns are limited to the epidermis. Second degree burns extend into the superficial papillary dermis. Third degree burns extend through the entire dermis. Fourth degree burns involve all the skin layers as well as the underlying muscle and bone.

Key Terms

  • avascular: Lacking blood vessels.
  • burn: A type of injury to flesh caused by heat, electricity, chemicals, light, radiation, or friction.
  • eschar: A dry, dark scab or scar, especially as a result of burning.

A burn is a type of injury to flesh caused by heat, electricity, chemicals, light, radiation, or friction. Most burns affect only the first two layers of the skin, the epidermis and dermis. Burns are classified by severity, surface area involvement, and depth of injury. In the latter system, burns are classified as first, second, third, or fourth degree burns based on the depth of injury to the dermis. Burns are also classified as major or minor depending on a combination of factors including age, thickness of burns, surface area of the body involved, and the presence of inhalation injury.

Types of Burns

First degree burns are limited to the epidermis. Second degree burns extend into the superficial papillary dermis. Third degree burns extend through the entire dermis. Fourth degree burns involve all the skin layers as well as the underlying muscle and bone.

This image shows a man's chest. It is very pink due to a minor sunburn.

First Degree Burn: Mild sunburn is an example of a first degree burn.

This image shows a second-degree burn on an upper arm, caused by a sunburn. The flesh is very pink and there is yellowish blistering.

Second Degree Burn: Serious sunburn is an example of a second degree burn.

This image shows a leg that is covered in third-degree burns. The lower part of the leg—from the knee all the way to the toes—has many circular shaped third-degree burns that are brown and yellow. In addition, some of the flesh is scorched black. The flesh that is not scorched—mainly on the ankle and upper foot—is very pink.

Third Degree Burn: Third degree burns to the lower leg with partial tissue charring.

This image shows an oval-shaped fourth-degree burn above the heel on the inside of the foot. The outer areas are brown, while the inside of the burn is yellow.

Fourth Degree Burn: Eight day old fourth degree burn on arch of foot caused by motorcycle muffler.

Consequences of Burns

While large burns can be fatal, modern treatments developed in the last 60 years have significantly improved the prognosis of such burns, especially in children and young adults. In the United States, approximately four out of every 100 people to suffer burns will die from their injuries. The majority of these fatalities occur either at the scene or on the way to hospital.

Infection is a major complication of burns. Infection is likely caused by impaired resistance from disruption of the skin’s mechanical integrity by the burn and generalized immune suppression. As a deep burn starts to heal, the skin barrier is replaced by eschar. This moist, protein-rich avascular environment encourages microbial growth. Migration of immune cells is hampered by destruction of the vasculature (blood vessels), and there is a release of inflammatory intermediaries that impede the immune response. Eschar also restricts distribution of systemically administered antibiotics because of its avascularity.

Allergies

An allergy is a hypersensitivity disorder of the immune system.

Learning Objectives

Evaluate the types and treatments of allergic reactions

Key Takeaways

Key Points

  • Allergy is one of four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity.
  • Mild allergies like hay fever are very common in the human population and cause symptoms such as red eyes, itchiness, runny nose, eczema, hives, or an asthma attack.
  • Treatments for allergies include avoiding known allergens, use of medications such as anti-histamines that specifically prevent allergic reactions, steroids that modify the immune system in general, and medications such as decongestants that reduce the symptoms.

Key Terms

  • anaphylaxis: A severe and rapid systemic allergic reaction to an allergen, causing a constriction of the trachea, preventing breathing; anaphylactic shock.
  • allergen: A substance which causes an allergic reaction.
  • patch test: A patch test is a method used to determine if a specific substance causes allergic inflammation of the skin.

An allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person’s immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid. Allergy is one of four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity. Allergic reactions are distinctive because of excessive activation of certain white blood cells called mast cells and basophils by a type of antibody called Immunoglobulin E (IgE). This reaction results in an inflammatory response that can range from uncomfortable to dangerous.

Mild allergies like hay fever are very common in the human population and cause symptoms such as red eyes, itchiness, runny nose, eczema, and hives. Allergies can play a major role in conditions such as asthma. In some people, severe allergies to environmental or dietary allergens or to medication may result in life-threatening reactions called anaphylaxis. Food allergies and reactions to the venom of stinging insects such as wasps and bees are often associated with these severe reactions.

Risk factors for allergy can be placed in two general categories: namely, host and environmental factors. Host factors include heredity, gender, race, and age, with heredity being by far the most significant. However, there have been recent increases in the incidence of allergic disorders that cannot be explained by genetic factors alone. Four major environmental candidates are alterations in exposure to infectious diseases during early childhood, environmental pollution, allergen levels, and dietary changes.

Allergy Tests

This image is of a young man receiving an allergy prick test. A blond-haired woman in a white lab coat sits on the right of the image. On her left is a young brown-haired man. His arm is out, and the woman, presumably a doctor, is pricking his skin with a tool. On the table in front of them is a tray of vials.

Allergy Testing: A patient receiving a skin allergy test.

A variety of tests exist to diagnose allergic conditions. Blood tests can be done to look for an allergen-specific IgE. Skin allergy testing is another method for medical diagnosis of allergies through the attempt to provoke a small, controlled, allergic response. A microscopic amount of an allergen (for example, tree pollen) is introduced to a patient’s skin by means of either a prick test, which employs a needle or pin to break the skin’s surface, or a patch test, where a patch containing the allergen is applied to the skin.

If an immuno-response is seen, it can be concluded that the patient has a hypersensitivity (or allergy) to that allergen. A response can take the the form of a rash (urticaria, also known as hives), or, worse—anaphylaxis (a serious reaction that can result in death). Further testing can then be performed in order to identify the specific allergen.

Allergy Treatments

Treatments for allergies include avoiding known allergens, use of medications such as antihistamines that specifically prevent allergic reactions, steroids that modify the immune system in general, and medications such as decongestants that reduce the symptoms. Many of these medications are taken by mouth; however, epinephrine, which is used to treat anaphylactic reactions, is injected. Immunotherapy employs the injection of allergens in order to gradually desensitize the body’s response.

Acne

Acne, clinically known as acne vulgaris, is a common human skin disease affecting the skin of the face, upper parts of the chest, and back.

Learning Objectives

Describe the development of acne

Key Takeaways

Key Points

  • Acne occurs most commonly during adolescence, and often continues into adulthood. For most people, acne diminishes over time and tends to disappear—or at the very least decreases—by age 25.
  • Acne develops as a result of blockages in hair follicles. Enlargement of sebaceous glands and an increase in sebum production occur with increased androgen production during puberty and directly before menstruation.
  • Sebaceous glands become clogged with sebum, a naturally occurring skin oil, and dead skin cells. Bacteria becomes trapped in these clogged follicles, producing pus and inflammation as the immune system attempts to destroy the bacteria. This buildup of pus results in a pimple.
  • The most common bacteria that causes acne is Propionibacterium acnes, an anaerobic bacteria that is part of the natural bacterial flora of the face.

Key Terms

  • androgen: A steroid hormone that stimulates or controls the development and maintenance of masculine characteristics in vertebrates.
  • dermabrasion: A cosmetic medical procedure in which the surface of the epidermis of the skin is removed by abrasion, typically to remove scarring or sun-damaged skin.
  • sebaceous gland: A gland of the skin that secretes an oily substance, sebum, usually into a hair follicle near the surface of the skin.
This image shows the sebaceous gland, hair follicle, sebum, skin surface, and hair. The sebaceous gland is deep underneath the skin's surface, adjacent to the hair follicle. The sebum clogs the sebaceous gland and hair follicle, pushing up to the skin surface.

Hair Follicle: The sebaceous gland produces oily secretions that can block the follicle, resulting in a pimple.

Acne, clinically known as acne vulgaris, is a common human skin disease affecting skin with the densest population of sebaceous follicles such as the face, upper parts of the chest, and back. Acne affects 40 to 50 million people of all racial and ethnic groups in the United States. Acne occurs most commonly during adolescence, and often continues into adulthood. For most people, acne diminishes over time and tends to disappear—or at the very least decreases—by age 25.

Development and Effects of Acne

Acne develops as a result of blockages in hair follicles. Enlargement of sebaceous glands and an increase in sebum production occur with increased androgen production during puberty and directly before menstruation. Sebaceous glands become clogged with sebum, a naturally occurring skin oil, and dead skin cells. Bacteria becomes trapped in these clogged follicles, producing pus and inflammation as the immune system attempts to destroy the bacteria. This buildup of pus results in a pimple. The most common bacteria that causes acne is Propionibacterium acnes, an anaerobic bacteria that is part of the natural bacterial flora of the face.

As acne heals, it can cause scarring. Aside from scarring, its main effects are psychological, such as reduced self-esteem and in very extreme cases, depression or suicide. Acne usually appears during adolescence, when people already tend to be most socially insecure.

This image shows a 14-year-old male with with acne on his forehead. Many different red pimples, of varying size and severity, dot this person's forehead.

Acne: Acne of a 14-year-old male during puberty.

Treatments for Acne

Many different treatments exist for acne including benzoyl peroxide, antibiotics, retinoids, antiseborrheic medications, anti-androgen medications, hormonal treatments, salicylic acid, alpha hydroxy acid, azelaic acid, nicotinamide, and keratolytic soaps. They are believed to work in at least four different ways, including: normalizing shedding into the pore to prevent clogging, killing Propionibacterium acnes, anti-inflammatory effects, and hormonal manipulation. Laser treatment and dermabrasion can be used to reduce the appearance of scarring caused by acne.