Among individuals being treated in intensive care units, the mortality rate is about 30-50% when systemic candidiasis develops.

"Candida" yeasts are generally present in healthy humans, frequently part of the human body's normal oral and intestinal flora, and particularly on the skin; however, their growth is normally limited by the human immune system and by competition of other microorganisms, such as bacteria occupying the same locations in the human body.

"Candida" requires moisture for growth, notably on the skin. For example, wearing wet swimwear for long periods of time is believed to be a risk factor. In extreme cases, superficial infections of the skin or mucous membranes may enter into the bloodstream and cause systemic "Candida" infections.

Factors that increase the risk of candidiasis include HIV/AIDS, mononucleosis, cancer treatments, steroids, stress, antibiotic usage, diabetes, and nutrient deficiency. Hormone replacement therapy and infertility treatments may also be predisposing factors. Treatment with antibiotics can lead to eliminating the yeast's natural competitors for resources in the oral and intestinal flora; thereby increasing the severity of the condition. A weakened or undeveloped immune system or metabolic illnesses are significant predisposing factors of candidiasis. Almost 15% of people with weakened immune systems develop a systemic illness caused by "Candida" species. Diets high in simple carbohydrates have been found to affect rates of oral candidiases.

"C. albicans" was isolated from the vaginas of 19% of apparently healthy women, i.e., those who experienced few or no symptoms of infection. External use of detergents or douches or internal disturbances (hormonal or physiological) can perturb the normal vaginal flora, consisting of lactic acid bacteria, such as lactobacilli, and result in an overgrowth of "Candida" cells, causing symptoms of infection, such as local inflammation. Pregnancy and the use of oral contraceptives have been reported as risk factors. Diabetes mellitus and the use of antibiotics are also linked to increased rates of yeast infections.

In penile candidiasis, the causes include sexual intercourse with an infected individual, low immunity, antibiotics, and diabetes. Male genital yeast infections are less common, but a yeast infection on the penis caused from direct contact via sexual intercourse with an infected partner is not uncommon.

Smoking, especially heavy smoking, is an important predisposing factor but the reasons for this relationship are unknown. One hypothesis is that cigarette smoke contains nutritional factors for "C. albicans", or that local epithelial alterations occur that facilitate colonization of candida species.

Malnutrition, whether by malabsorption, or poor diet, especially hematinic deficiencies (iron, vitamin B12, folic acid) can predispose to oral candidiasis, by causing diminished host defense and epithelial integrity. For example, iron deficiency anemia is thought to cause depressed cell-mediated immunity. Some sources state that deficiencies of vitamin A or pyridoxine are also linked.

There is limited evidence that a diet high in carbohydrates predisposes to oral candidiasis. "In vitro" and studies show that Candidal growth, adhesion and biofilm formation is enhanced by the presence of carbohydrates such as glucose, galactose and sucrose.

While infections may occur without sex, a high frequency of intercourse increases the risk. Personal hygiene methods or tight-fitting clothing, such as tights and thong underwear, do not appear to increase the risk.

In pregnancy, higher levels of estrogen make a woman more likely to develop a yeast infection. During pregnancy, the "Candida" fungus is more common, and recurrent infection is also more likely. There is tentative evidence that treatment of asymptomatic candidal vulvovaginitis in pregnancy reduces the risk of preterm birth.

Patients with the following conditions, treatments or situations are at increased risk for invasive candidiasis.

- Critical illness

- Long-term intensive care unit stay

- Abdominal surgery (aggravated by anastomotic leakage or repeat laparotomies)

- Immunosuppressive diseases

- Acute necrotizing pancreatitis

- Malignant hematologic disease

- Solid-organ transplantation

- Hematopoietic stem cell transplantation

- Solid-organ tumors

- Neonates (especially low birth weight and preterm infants)

- Broad-spectrum antibiotic treatment

- Central venous catheter

- Internal prosthetic device

- Total parenteral nutrition

- Hemodialysis

- Glucocorticoid use

- Chemotherapy

- Noninvasive "Candida" colonization (particularly if multifocal)

Invasive candidiasis is a nosocomial infection with the majority of cases associated with hospital stays.

Esophageal candidiasis is an opportunistic infection of the esophagus by "Candida albicans". The disease usually occurs in patients in immunocompromised states, including post-chemotherapy and in AIDS. However, it can also occur in patients with no predisposing risk factors, and is more likely to be asymptomatic in those patients. It is also known as candidal esophagitis or monilial esophagitis.

Several drugs may cause AC as a side effect, by various mechanisms, such as creating drug-induced xerostomia. Various examples include isotretinoin, indinavir, and sorafenib. Isotretinoin (Accutane), an analog of vitamin A, is a medication which dries the skin. Less commonly, angular cheilitis is associated with primary hypervitaminosis A, which can occur when large amounts of liver (including cod liver oil and other fish oils) are regularly consumed or as a result from an excess intake of vitamin A in the form of vitamin supplements. Recreational drug users may develop AC. Examples include cocaine, methamphetamines, heroin, and hallucinogens.

Systemic mycoses due to opportunistic pathogens are infections of patients with immune deficiencies who would otherwise not be infected. Examples of immunocompromised conditions include AIDS, alteration of normal flora by antibiotics, immunosuppressive therapy, and metastatic cancer. Examples of opportunistic mycoses include Candidiasis, Cryptococcosis and Aspergillosis.

Systemic mycoses due to primary pathogens originate primarily in the lungs and may spread to many organ systems. Organisms that cause systemic mycoses are inherently virulent. In general primary pathogens that cause systemic mycoses are dimorphic.

Some systemic disorders are involved in angular cheilitis by virtue of their association with malabsorption and the creation of nutritional deficiencies described above. Such examples include people with anorexia nervosa. Other disorders may cause lip enlargement (e.g. orofacial granulomatosis), which alters the local anatomy and extenuates the skin folds at the corners of the mouth. More still may be involved because they affect the immune system, allowing normally harmless organisms like Candida to become pathogenic and cause an infection. Xerostomia (dry mouth) is thought to account for about 5% of cases of AC. Xerostomia itself has many possible causes, but commonly the cause may be side effects of medications, or conditions such as Sjögren's syndrome. Conversely, conditions which cause drooling or sialorrhoea (excessive salivation) can cause angular cheilitis by creating a constant wet environment in the corners of the mouth. About 25% of people with Down syndrome appear to have AC. This is due to relative macroglossia, an apparently large tongue in a small mouth, which may constantly stick out of the mouth causing maceration of the corners of the mouth with saliva. Inflammatory bowel diseases (such as Crohn's disease or ulcerative colitis) can be associated with angular cheilitis. In Crohn's, it is likely the result of malabsorption and immunosuppressive therapy which gives rise to the sores at the corner of the mouth. Glucagonomas are rare pancreatic endocrine tumors which secrete glucagon, and cause a syndrome of dermatitis, glucose intolerance, weight loss and anemia. AC is a common feature of glucagonoma syndrome. Infrequently, angular cheilitis may be one of the manifestations of chronic mucocutaneous candidiasis, and sometimes cases of oropharyngeal or esophageal candidiasis may accompany angular cheilitis. Angular cheilitis may be present in human immunodeficiency virus infection, neutropenia, or diabetes. Angular cheilitis is more common in people with eczema because their skin is more sensitive to irritants. Other conditions possibly associated include plasma cell gingivitis, Melkersson-Rosenthal syndrome, or sideropenic dysphagia (also called Plummer-Vinson syndrome or Paterson-Brown-Kelly syndrome).

Acute paronychia is usually caused by bacteria. Claims have also been made that the popular acne medication, isotretinoin, has caused paronychia to develop in patients. Paronychia is often treated with antibiotics, either topical or oral. Chronic paronychia is most often caused by a yeast infection of the soft tissues around the nail but can also be traced to a bacterial infection. If the infection is continuous, the cause is often fungal and needs antifungal cream or paint to be treated.

Risk factors include repeatedly washing hands and trauma to the cuticle such as may occur from biting. In the context of bartending, it is known as "bar rot".

Prosector's paronychia is a primary inoculation of tuberculosis of the skin and nails, named after its association with prosectors, who prepare specimens for dissection. Paronychia around the entire nail is sometimes referred to as "runaround paronychia".

Painful paronychia in association with a scaly, erythematous, keratotic rash (papules and plaques) of the ears, nose, fingers, and toes may be indicative of acrokeratosis paraneoplastica, which is associated with squamous cell carcinoma of the larynx.

Paronychia can occur with diabetes, drug-induced immunosuppression, or systemic diseases such as pemphigus.

Since opportunistic infections can cause severe disease, much emphasis is placed on measures to prevent infection. Such a strategy usually includes restoration of the immune system as soon as possible, avoiding exposures to infectious agents, and using antimicrobial medications ("prophylactic medications") directed against specific infections.

Vulvovaginitis in children may be "nonspecific", or caused by irritation with no known infectious cause, or infectious, caused by a pathogenic organism. Nonspecific vulvovaginitis may be triggered by fecal contamination, sexual abuse, chronic diseases, foreign bodies, nonestrogenized epithelium, chemical irritants, eczema, seborrhea, or immunodeficiency. It is treated with topical steroids; antibiotics may be given in cases where itching has resulted in a secondary infection.

Infectious vulvovaginitis can be caused by group A beta-hemolytic "Streptococcus" (7-20% of cases), "Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, Shigella, Yersinia", or common STI organisms ("Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis", herpes simplex virus, and human papillomavirus)"." Symptoms and treatment of infectious vulvovaginitis vary depending on the organism causing it. "Shigella" infections of the reproductive tract usually coexist with infectious of the gastrointestinal tract and cause mucous, purulent discharge. They are treated with trimethoprim-sulfamethoxazole. "Streptococcus" infections cause similar symptoms to nonspecific vulvovaginitis and are treated with amoxicillin. STI-associated vulvovaginitis may be caused by sexual abuse or vertical transmission, and are treated and diagnosed like adult infections.

The current first-line treatment is fluconazole, 200 mg. on the first day, followed by daily dosing of 100 mg. for at least 21 days total. Treatment should continue for 14 days after relief of symptoms.

Other therapy options include:

- nystatin is not an effective treatment for esophageal candidiasis. It can be used as (swish, do not swallow) treatment for oral candidiasis that occurs with the use of asthma pumps.

- other oral triazoles, such as itraconazole

- caspofungin, used in refractory or systemic cases

- amphotericin, used in refractory or systemic cases

Otomycosis is treated by debridment followed with topical azole antifungals, and symptomatically managed with oral antihistamines. Per a study in Iran 10cc acetic acid 2% plus 90 cc of isopropyl alcohol 70% was effective.

Individuals at higher risk are often prescribed prophylactic medication to prevent an infection from occurring. A patient's risk level for developing an opportunistic infection is approximated using the patient's CD4 T-cell count and sometimes other markers of susceptibility. Common prophylaxis treatments include the following:

The oral lesion itself is benign and self-limiting, however this may not necessarily be the case for the underlying cause of immunocompromise. For instance, OHL with HIV/AIDS is a predictor of bad prognosis, (i.e. severe immunosuppression and advanced disease).

Vaginitis is the disruption of the healthy vaginal microbiota. The vaginal microbiota consists of those organisms which generally do not cause symptoms, infections, and results in good pregnancy outcomes, and is dominated mainly by Lactobacillus species. The disruption of the normal microbiota can cause a vaginal yeast infection. Vaginal yeast infection can affect women of all ages and is very common. The yeast "Candida albicans" is the most common cause of vaginitis. Specific forms of vaginal inflammation include the following types:

Infectious vaginitis accounts for 90% of all cases in reproductive age women:

- Candidiasis: vaginitis caused by proliferation of "Candida albicans", "Candida tropicalis", "Candida krusei"

- Bacterial vaginosis: vaginitis caused by increased growth of "Gardnerella" (a bacterium).

- Aerobic vaginitis

Other less common infections are caused by gonorrhea, chlamydia, "Mycoplasma", herpes, "Campylobacter", improper hygiene, and some parasites, notably "Trichomonas vaginalis". Women who have diabetes develop infectious vaginitis more often than women who do not.

Vaginal infections often have multiple causes (varies between countries between 20 and 40% of vaginal infections), which present challenging cases for treatment. Indeed, when only one cause is treated, the other pathogens can become resistant to treatment and induce relapses and recurrences. Therefore, the key factor is to get a precise diagnosis and treat with broad spectrum anti-infective agents (often also inducing adverse effects).

Further, either a change in pH balance or introduction of foreign bacteria in the vagina can lead to infectious vaginitis. Physical factors that have been claimed to contribute to the development of infections include the following: constantly wet vulva due to tight clothing, chemicals coming in contact with the vagina via scented tampons, antibiotics, birth control pills, or a diet favoring refined sugar and yeast.

Denture-related stomatitis is usually a harmless condition with no long term consequences. It usually resolves with simple measures such as improved denture hygiene or topical antifungal medication. In severely immunocompromised individuals (e.g. those with HIV), the infection may present a more serious threat.

Paronychia may be divided as follows:

- "Acute paronychia" is an infection of the folds of tissue surrounding the nail of a finger or, less commonly, a toe, lasting less than six weeks. The infection generally starts in the paronychium at the side of the nail, with local redness, swelling, and pain. Acute paronychia is usually caused by direct or indirect trauma to the cuticle or nail fold, and may be from relatively minor events, such as dishwashing, an injury from a splinter or thorn, nail biting, biting or picking at a hangnail, finger sucking, an ingrown nail, or manicure procedures.

- "Chronic paronychia" is an infection of the folds of tissue surrounding the nail of a finger or, less commonly, a toe, lasting more than six weeks. It is a nail disease prevalent in individuals whose hands or feet are subject to moist local environments, and is often due to contact dermatitis. In chronic paronychia, the cuticle separates from the nail plate, leaving the region between the proximal nail fold and the nail plate vulnerable to infection. It can be the result of dish washing, finger sucking, aggressively trimming the cuticles, or frequent contact with chemicals (mild alkalis, acids, etc.).

Alternatively, paronychia may be divided as follows:

- "Candidal paronychia" is an inflammation of the nail fold produced by "Candida albicans".

- "Pyogenic paronychia" is an inflammation of the folds of skin surrounding the nail caused by bacteria. Generally acute paronychia is a pyogenic paronychia as it is usually caused by a bacterial infection.

Otomycosis is a fungal ear infection, a superficial mycotic infection of the outer ear canal. It is more common in the tropical countries. The infection may be either subacute or acute and is characterized by malodorous discharge, inflammation, pruritus, scaling, and severe discomfort. Suppuration can occur due to superimposed bacterial infection commonly due to pseudomonas species and proteus species. The mycosis results in inflammation, superficial epithelial exfoliation, masses of debris containing hyphae, suppuration, and pain.

The major risk factor for the development of this condition is wearing an upper complete denture, particularly when it is not removed during sleep and cleaned regularly. Older dentures are more likely to be involved. Other factors include xerostomia (dry mouth), diabetes or a high carbohydrate diet. Human immunodeficiency virus (HIV) can rarely be an underlying factor.

Wearing dental appliances such as dentures alters the oral microbiota. A microbial plaque composed of bacteria and/or yeasts forms on the fitting surface of the denture (the surface which rests against the palate) and on the mucosa which is covered. Over time, this plaque may be colonized by Candida species. The local environment under a denture is more acidic and less exposed to the cleansing action of saliva, which favors high Candida enzymatic activity and may cause inflammation in the mucosa. "C. albicans" is the most commonly isolated organism, but occasionally bacteria are implicated.

There is controversy as to whether this condition represents a true infection by "C. albicans" or just a reaction to the various micro-organisms present underneath a denture. It has been reported that often the surface of the denture shows positive culture for "Candida" but biospsies of the mucosa rarely show hyphae invading epithelium. Similarly, microbiologic swabs of the involved mucosa show a much less heavy colonization than the surface of the denture. This has led some to conclude that the defining feature of a true infection is absent in denture-related stomatitis.

Poorly fitting dentures may cause pressure on the mucosa and mechanical irritation may create a similar clinical appearance, but this is uncommon. An orthodontic appliance may uncommonly produce a similar result. However, mucosal trauma is thought increase the ability of "C. albicans" to invade the tissues.

Aside from infection and mechanical trauma, inflammatory reactions of the mucosa beneath a denture can also result from irritation or allergy (allergic contact stomatitis) caused by the materials in the denture itself (acrylic, cobalt, chromium), or in response to substances within denture adhesives. Incomplete curing of the acrylic resin (the prosthetic material) may also be an involved factor.