Boils
Classification and external resources
Furuncle
ICD-10	L02
ICD-9	680.9
ICD-O:	M20.t/{{{2}}}
DiseasesDB	29434
MedlinePlus	001474 000825
MeSH	D005667

A boil, also called a furuncle, is a deep folliculitis, infection of the hair follicle. It is most commonly caused by infection by the bacterium Staphylococcus aureus , resulting in a painful swollen area on the skin caused by an accumulation of pus and dead tissue.^[1] Individual boils clustered together are called carbuncles.^[2] Most human infections are caused by coagulase-positive S. aureus strains, notable for the bacteria's ability to produce coagulase, an enzyme that can clot blood. Almost any organ system can be infected by S. aureus.

  Signs and issues

Boils are bumpy red, pus-filled lumps around a hair follicle that are tender, warm, and very painful. They range from pea-sized to golf ball-sized. A yellow or white point at the center of the lump can be seen when the boil is ready to drain or discharge pus. In a severe infection, an individual may experience fever, swollen lymph nodes, and fatigue. A recurring boil is called chronic furunculosis.^[1][3][4][5] Skin infections tend to be recurrent in many patients and often spread to other family members. Systemic factors that lower resistance commonly are detectable, including: diabetes, obesity, and hematologic disorders.^[6]

  Causes

Usually, the cause is bacteria such as staphylococci that are present on the skin. Bacterial colonization begins in the hair follicles and can cause local cellulitis and inflammation.^[1][4][5] Additionally, myiasis caused by the Tumbu fly in Africa usually presents with cutaneous furuncles.^[7] Risk factors for furunculosis include bacterial carriage in the nostrils, diabetes mellitus, obesity, lymphoproliferative neoplasms, malnutrition, and use of immunosuppressive drugs.^[8] Patients with recurrent boils are as well more likely to have a positive family history, take antibiotics, and to have been hospitalized, anemic, or diabetic; they are also more likely to have associated skin diseases and multiple lesions.^[9]

  Complications

The most common complications of boils are scarring and infection or abscess of the skin, spinal cord, brain, kidneys, or other organs. Infections may also spread to the bloodstream (sepsis) and become life-threatening.^[4][5] S. aureus strains first infect the skin and its structures (for example, sebaceous glands, hair follicles) or invades damaged skin (cuts, abrasions). Sometimes the infections are relatively limited (such as a stye, boil, furuncle, or carbuncle), but other times they may spread to other skin areas (causing cellulitis, folliculitis, or impetigo). Unfortunately, these bacteria can reach the bloodstream (bacteremia) and end up in many different body sites, causing infections (wound infections, abscesses, osteomyelitis, endocarditis, pneumonia)^[10] that may severely harm or kill the infected person. S. aureus strains also produce enzymes and exotoxins that likely cause or increase the severity of certain diseases. Such diseases include food poisoning, septic shock, toxic shock syndrome, and scalded skin syndrome.^[11] Almost any organ system can be infected by S. aureus.

  Treatment

In contrast to common belief, boils do not need to be drained in order to heal; in fact opening the affected skin area can cause further infections.^[12] In some instances, however, draining can be encouraged by application of a cloth soaked in warm salt water. Washing and covering the furuncle with antibiotic cream or antiseptic tea tree oil^[13] and a bandage also promotes healing. Furuncles should never be squeezed or lanced without the oversight of a medical practitioner because it may spread the infection.^[1][5]

Furuncles at risk of leading to serious complications should be incised and drained by a medical practitioner. These include furuncles that are unusually large, last longer than two weeks, or are located in the middle of the face or near the spine.^[1][5]

Antibiotic therapy is advisable for large or recurrent boils or those that occur in sensitive areas (such as around or in the nostrils or in the ear).^[1][3][4][5] Staphylococcus aureus has the ability to acquire antimicrobial resistance easily, making treatment difficult. Knowledge of the antimicrobial resistance of S. aureus is important in the selection of antimicrobials for treatment.^[14] Poor personal hygiene being common, the role of nasal S. aureus carrier may differ from communities with good hygienic practices. Staphylococcus aureus re-infection may result from contact with infected family members, contaminated fomites, or from other extra-nasal sites. This raises a suggestion to treat household contacts and close contacts if recurrence persists, because it is likely that one or more contacts are asymptomatic carriers of S. aureus. In addition to the increase in the cost of treatment in poor countries, the possibility of developing drug resistance must be considered. The most important independent predictor of recurrence is a positive family history. Boils are spread among individuals by touching or bursting a boil. Furunculosis is a common disease, particularly with deficient hygiene. A large number of S. aureus organisms are frequently present on the sheets and underclothing of patients with furunculosis and may cause re-infection of patients and infection of other members of the family.^[9] The role of iron deficiency anemia in recurrent furunculosis was demonstrated, all patients were free from recurrence during the six months follow-up period after iron supplementation.^[15] A variety of host factors, such as abnormal neutrophil chemotaxis, deficient intra-cellular killing, and immuno-deficient states are of importance in a minority of patients with recurrent furunculosis.^[16] Health education about sound personal hygiene and correction of anemia should be mandatory in management of furunculosis.^[9] It was found that recurrence was significantly associated with poor personal hygiene.^[17] A previous study reported that MRSA infection was significantly associated with poor personal hygiene. It was reported that frequent hand and body washing with water and antimicrobial soap solution decreases staphylococcus skin colonization. Previous use of antibiotics is associated with a high risk of recurrence. This may be due to the development of resistance to the antibiotics used.^[18] An associated skin disease favors recurrence. This may be attributed to the persistent colonization of abnormal skin with S. aureus strains, such as is the case in patients with atopic dermatitis.^[18]

  See also

• Japanese spotted fever
• List of cutaneous conditions

  References

  External links

Wikimedia Commons has media related to: Furuncles

• DermAtlas 1817374494

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2009)

Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environmental pressure. While below the boiling point a liquid evaporates from its surface, at the boiling point vapor bubbles come from the bulk of the liquid. For this to be possible, the vapor pressure must be sufficiently high to win the atmospheric pressure, so that the bubbles can be "inflated". Thus, the difference between evaporation and boiling is "mechanical", rather than thermodynamical. The boiling point is lowered when the pressure of the surrounding atmosphere is reduced, for example by the use of a vacuum pump or at high altitudes. Boiling occurs in three characteristic stages, which are nucleate, transition and film boiling. These stages generally take place from low to high heating surface temperatures, respectively.

  Nucleate boiling

Nucleate boiling is characterized by the growth of bubbles or pops on a heated surface, which rise from discrete points on a surface, whose temperature is only slightly above the liquid’s. In general, the number of nucleation sites are increased by an increasing surface temperature.

An irregular surface of the boiling vessel (i.e. increased surface roughness) can create additional nucleation sites, while an exceptionally smooth surface, such as plastic, lends itself to superheating. Under these conditions, a heated liquid may show boiling delay and the temperature may go somewhat above the boiling point without boiling.

  Transition boiling

Transition boiling may be defined as the unstable boiling, which occurs at surface temperatures between the maximum attainable in nucleate and the minimum attainable in film boiling.

The formation of bubbles in a heated liquid is a complex physical process which often involves cavitation and acoustic effects, such as the broad-spectrum hiss one hears in a kettle not yet heated to the point where bubbles boil to the surface.

  Film boiling

If a surface heating the liquid is significantly hotter than the liquid then film boiling will occur, where a thin layer of vapor, which has low thermal conductivity, insulates the surface. This condition of a vapor film insulating the surface from the liquid characterizes film boiling.

  Applications

  Distillation

In distillation, boiling is used in separating mixtures. This is possible because the vapor rising from a boiling fluid generally has a ratio of components different from that in the liquid.

  Boiling for water sterilization

Boiling can be used as a method of water disinfection but is only advocated as an emergency water treatment method, or as a method of portable water purification in rural or wilderness settings without access to a potable water infrastructure. Bringing water to the boil is effective in killing or inactivating most bacteria, viruses and pathogens. Boiling is the most certain way of killing nearly all microorganisms. According to the Wilderness Medical Society^[1], water temperatures above 160°F (70°C) kill all pathogens within 30 minutes and above 185°F (85°C) within a few minutes. So in the time it takes for the water to reach the boiling point (212°F or 100°C) from 160°F (70°C), all pathogens will be killed, even at high altitude. To be extra safe, let the water boil rapidly for one minute, especially at higher altitudes since water boils at a lower temperature.^[1]

  Boiling in cooking

  Transition boiling of water

In cooking, boiling is the method of cooking food in boiling water, or other water-based liquid such as stock or milk. Simmering is gentle boiling, while in poaching the cooking liquid moves but scarcely bubbles.

Boiling is a very harsh technique of cooking. Delicate foods such as fish cannot be cooked in this fashion because the bubbles can damage the food. Foods such as red meat, chicken, and root vegetables can be cooked with this technique because of their tough texture.

The boiling point of water is typically considered to be 100 °C or 212 °F. Pressure and a change in composition of the liquid may alter the boiling point of the liquid. For this reason, high elevation cooking generally takes longer since boiling point is a function of atmospheric pressure. In Denver, Colorado, which is at an elevation of about one mile, water boils at approximately 95 °C.^[2] Depending on the type of food and the elevation, the boiling water may not be hot enough to cook the food properly. Similarly, increasing the pressure as in a pressure cooker raises the temperature of the contents above the open air boiling point.

Adding a water soluble substance, such as salt or sugar also increases the boiling point. This is called boiling-point elevation. At palatable concentrations of salt, the effect is very small, and the boiling point elevation is difficult to notice. However, while making thick sugar syrup, such as for Gulab Jamun, one will notice boiling point elevation. Due to variations in composition and pressure, the boiling point of water is almost never exactly 100 °C, but rather close enough for cooking.

Bringing water to a boil is generally done by applying maximal heat, then shutting off when the water has come to a boil, which is known as bang–bang control. Keeping water at or below a boil requires more careful control of temperature, particularly by using feedback.

In places where the available water supply is contaminated with disease-causing bacteria, boiling water and allowing it to cool before drinking it is practiced as a valuable health measure. Boiling is the most certain way of killing all microorganisms in emergency situations.

Foods suitable for boiling include vegetables, starchy foods such as rice, noodles and potatoes, eggs, meats, sauces, stocks and soups.

Boiling has several advantages. It is safe and simple, and it is appropriate for large-scale cookery. Older, tougher, cheaper cuts of meat and poultry can be made digestible. Nutritious, well flavoured stock is produced. Also, maximum color and nutritive value is retained when cooking green vegetables, provided boiling time is kept to the minimum.

On the other hand, there are several disadvantages. There is a loss of soluble vitamins from foods to the water (if the water is discarded), and some boiled foods can look unattractive. Boiling can also be a slow method of cooking food.

Boiling can be done in several ways: The food can be placed into already rapidly boiling water and left to cook, the heat can be turned down and the food can be simmered; or the food can also be placed into the pot, and cold water may be added to the pot. This may then be boiled until the food is satisfactory.

Water on the outside of a pot, i.e. a wet pot, increases the time it takes the pot of water to boil. The pot will heat at a normal rate once all excess water on the outside of the pot evaporates.

  Levels of boiling

In Chinese cuisine, particularly tea brewing, one distinguishes five stages of boiling:^[3] "shrimp eyes, the first tiny bubbles that start to appear on the surface of the kettle water, crab eyes, the secondary, larger bubbles, then fish eyes, followed by rope of pearls, and finally raging torrent [rolling boil]".

In detail:^[4]

shrimp eyes

about 70-80 °C (155–175 °F) – separate bubbles, rising to top

crab eyes

about 80 °C (175 °F) – streams of bubbles

fish eyes

about 80-90 °C (175–195 °F) – larger bubbles

rope of pearls

about 90-95 °C (195–205 °F) – steady streams of large bubbles

raging torrent

rolling boil, swirling and roiling

  See also

Look up boiling in Wiktionary, the free dictionary.

Wikibooks Cookbook has a recipe/module on Boiling

• Nucleate boiling
• Phase diagram
• Phase transition
• Boiling point

  References