Superficial scrapes of skin examined underneath a microscope may reveal the presence of a fungus. This is done by utilizing a diagnostic method called KOH Test, wherein the skin scrapings are placed on a slide and immersed on a dropful of potassium hydroxide solution to dissolve the keratin on the skin scrappings thus leaving fungal elements such as hyphae, septate or yeast cells viewable. If the skin scrapings are negative and a fungus is still suspected, the scrapings are sent for culture. Because the fungus grows slowly, the culture results do take several days to become positive.

Advice often given includes:

- Avoid sharing clothing, sports equipment, towels, or sheets.

- Wash clothes in hot water with fungicidal soap after suspected exposure to ringworm.

- Avoid walking barefoot; instead wear appropriate protective shoes in locker rooms and sandals at the beach.

- Avoid touching pets with bald spots, as they are often carriers of the fungus.

When visiting a doctor, the basic diagnosis procedure applies. This includes checking the patient's medical history and medical record for risk factors, a medical interview during which the doctor asks questions (such as about itching and scratching), and a physical examination. Athlete's foot can usually be diagnosed by visual inspection of the skin and by identifying less obvious symptoms such as itching of the affected area.

If the diagnosis is uncertain, direct microscopy of a potassium hydroxide preparation of a skin scraping (known as a KOH test) can confirm the diagnosis of athlete's foot and help rule out other possible causes, such as candidiasis, pitted keratolysis, erythrasma, contact dermatitis, eczema, or psoriasis. Dermatophytes known to cause athlete's foot will demonstrate multiple septate branching hyphae on microscopy.

A Wood's lamp (black light), although useful in diagnosing fungal infections of the scalp (tinea capitis), is not usually helpful in diagnosing athlete's foot, since the common dermatophytes that cause this disease do not fluoresce under ultraviolet light.

Because fungi prefer warm, moist environments, preventing ringworm involves keeping skin dry and avoiding contact with infectious material. Basic prevention measures include:

- Washing hands after handling animals, soil, and plants.

- Avoiding touching characteristic lesions on other people.

- Wearing loose-fitting clothing.

- Practicing good hygiene when participating in sports that involve physical contact with other people.

no approved human vaccine exist against "Dermatophytosis". For horses, dogs and cats there is available an approved inactivated vaccine called "Insol Dermatophyton" (Boehringer Ingelheim) which provides time-limited protection against several trichophyton and microsporum fungal strains.

Tinea capitis may be difficult to distinguish from other skin diseases that cause scaling, such as psoriasis and seborrhoeic dermatitis; the basis for the diagnosis is positive microscopic examination and microbial culture of epilated hairs. Wood's lamp (blacklight) examination will reveal bright green to yellow-green fluorescence of hairs infected by "M. canis", "M. audouinii", "M. rivalieri", and "M. ferrugineum" and a dull green or blue-white color of hairs infected by "T. schoenleinii". Individuals with "M. canis" infection trichoscopy will show characteristic small comma hairs. Histopathology of scalp biopsy shows fungi sparsely distributed in the stratum corneum and hyphae extending down the hair follicle, placed on the surface of the hair shaft. These findings are occasionally associated with inflammatory tissue reaction in the local tissue.

Tinea cruris is similar to, but different from Candidal intertrigo, which is an infection of the skin by "Candida albicans". The latter is more specifically located between intertriginous folds of adjacent skin, which can be present in the groin or scrotum, and be indistinguishable from fungal infections caused by "tinea". However, candidal infections tend to both appear and with treatment disappear more quickly. It may also affect the scrotum.

Medical professionals recommend a preventative based approach of stopping fungus before it occurs. Prevention is preferable over a reactive treatment approach. The preventative based approach involves removing heat and moisture to the groin area.

- Dry off with a clean towel immediately after showering, swimming or perspiring.

- Shower after physical activities.

- Wear underwear with high air and moisture permeability fabric, such as linen (flax).

There are several preventive foot hygiene measures that can prevent athlete's foot and reduce recurrence. Some of these include keeping the feet dry, clipping toenails short; using a separate nail clipper for infected toenails; using socks made from well-ventilated cotton or synthetic moisture wicking materials (to soak moisture away from the skin to help keep it dry); avoiding tight-fitting footwear, changing socks frequently; and wearing sandals while walking through communal areas such as gym showers and locker rooms.

According to the Centers for Disease Control and Prevention, "Nails should be clipped short and kept clean. Nails can house and spread the infection." Recurrence of athlete's foot can be prevented with the use of antifungal powder on the feet.

The fungi (molds) that cause athlete's foot require warmth and moisture to survive and grow. There is an increased risk of infection with exposure to warm, moist environments (e.g., occlusive footwear—shoes or boots that enclose the feet) and in shared humid environments such as communal showers, shared pools, and treatment tubs. Chlorine bleach is a disinfectant and common household cleaner that kills mold. Cleaning surfaces with a chlorine bleach solution prevents the disease from spreading from subsequent contact. Cleaning bathtubs, showers, bathroom floors, sinks, and counters with bleach helps prevent the spread of the disease, including reinfection.

Keeping socks and shoes clean (using bleach in the wash) is one way to prevent fungi from taking hold and spreading. Avoiding the sharing of boots and shoes is another way to prevent transmission. Athlete's foot can be transmitted by sharing footwear with an infected person. Hand-me-downs and purchasing used shoes are other forms of shoe-sharing. Not sharing also applies to towels, because, though less common, fungi can be passed along on towels, especially damp ones.

There are differential diagnosis' for erythrasma which includes psoriasis, candidasis, dermaphytosis, and interigo. The diagnosis can be made on the clinical picture alone. However, a simple side-room investigation with a Wood's lamp is additionally useful in diagnosing erythrasma. The ultraviolet light of a Wood's lamp causes the organism to fluoresce a characteristic coral red color, differentiating it from other skin conditions such as tinea versicolor, which may fluoresce a copper-orange color. Another route to differentiate erythrasma would be through bacterial and mycology related cultures to compare/contrast normal results to these findings. These are both non-invasive routes.

Erythrasma is often mistakenly diagnosed as dermatophytic infection which is a fungal infection and not a bacterial infection. The difference here is that fungi are multicellular and eukaryotes while bacteria are single celled prokaryotes. This is vital to differentiate because of the way they reproduce will indicate how the infection will spread throughout the human body.

The treatment of choice by dermatologists is a safe and inexpensive oral medication, griseofulvin, a secondary metabolite of the fungus "Penicillium griseofulvin". This compound is "fungistatic" (inhibiting the growth or reproduction of fungi) and works by affecting the microtubular system of fungi, interfering with the mitotic spindle and cytoplasmic microtubules. The recommended pediatric dosage is 10 mg/kg/day for 6–8 weeks, although this may be increased to 20 mg/kg/d for those infected by "T. tonsurans", or those who fail to respond to the initial 6 weeks of treatment. Unlike other fungal skin infections that may be treated with topical therapies like creams applied directly to the afflicted area, griseofulvin must be taken orally to be effective; this allows the drug to penetrate the hair shaft where the fungus lives. The effective therapy rate of this treatment is generally high, in the range of 88–100%.

Other oral antifungal treatments for tinea capitis also frequently reported in the literature include terbinafine, itraconazole, and fluconazole; these drugs have the advantage of shorter treatment durations than griseofulvin. However, concern has been raised about the possibility of rare side effects like liver toxicity or interactions with other drugs; furthermore, the newer drug treatments tend to be more expensive than griseofulvin.

On September 28, 2007, the U.S. Food and Drug Administration stated that Lamisil (Terbinafine hydrochloride, by Novartis AG) is a new treatment approved for use by children aged 4 years and older. The antifungal can be sprinkled on a child's food to treat the infection. Lamisil carries hepatotoxic risk, and can cause a metallic taste in the mouth.

Recent research for Erythrasma is mainly focused on the treatments and which methods work best to treat the patient depending on the severity of the condition. In a 2016 study performed by Prathyusha Prabhakar and H. Hema, they looked into comparing 2% clotrimazole cream and 2% Fusidic cream in treating erythrasma. This was a one year long hospital based study in South India that resulted in stating that the groin was the most common site for the symptoms of itching and discloloration being predominant and also mostly in men. The general conclusion made was that topical 2% fusidic acid cream was found to be more effective than 2% clotrimazole cream in patients with erythrasma. The topical 2% clotrimazole cream was more effective only when an associated fungal infection was present.

Another study performed in early 2017 by Tanya Grewal and Philip Cohen looked directly at mupirocin 2% ointment monotherapy. This study was done with nine males who showed a presence of erythrasma at bilateral inguinal folds, medial thighs, and axillae. After initial diagnosis by Wood lamp's examination to confirm the diagnosis, the antibiotic cream was distributed. Mupirocin is a topical antibiotic that is usually used to treat Streptococcus and Staphylococcus infections. After 2-4 weeks of use, the erythrasma seemed to clear up. They were able to conclude that the application of 2% Mupirocin ointment monotherapy twice a day, everyday is a great consideration for a first line of treatment for erythrasma.

A study done in 2011 by M. Inci and G. Serarslan revolved around detecting the frequency and risk factors of interdigital erythrasma in patients who were possibly diagnosed with Tinea pedis. The study was done with 122 people who had a confirmed diagnoses of erythrasma through the Wood's lamp method. The results showed that erythrasma was more prevalent in males who were over the age of 40 years. Their conclusions were that erythrasma is a common condition and can also easily mimic other infections such as tinea pedis and that gram staining is a better tool to differentiate the bacteria and it's mechanism than the Wood's lamp method.

Guttate psoriasis can typically be diagnosed by clinical examination alone. If necessary, a skin biopsy can be used to support the diagnosis.

Guttate psoriasis accounts for approximately 2% of psoriasis cases.

The diagnoses of geotrichosis cannot be determined without using culture or microscopic measurements. The laboratory diagnosis of geotrichosis involves collected fungi samples areas of infections without contamination. Scraping of the mouth lesions and the ulcers can provide a sample of "G. candidum." Samples can also be collected from pus and mucus can be obtained from the feces. Sputum can be searched for the mucoid-like white flakes for further examination. Culturing the cylindrical barrel-shaped or elliptical fungi in considerable numbers in oral lesions is an indicator that a patient may have geotrichosis. Under the microscope the fungi appears yeast-like and septate branching hyphae that can be broken down into chains or individual arthrospores. Arthrospores appear rectangular with flat or rounded ends. Under the microscope the arthroconidia size range from 6-12μm x 3-6μm. Arthroconidia and coarse true hyphae can be observed can be observed under the microscope. Another identification method for "G. candidum" is selective isolation method. A selection isolation method based on the fungi tolerance to novobiocin and carbon dioxide can determine if "G. candidum" is the cause of illness.

With no particular affinity to any particular ethnic group, seen in all age groups and equally amongst males and females, the precise prevalence is not known.

CLM can be treated in a number of different ways:

- Systemic (oral) agents include albendazole (trade name "Albenza") and ivermectin (trade name "Stromectol")).

- Another agent which can be applied either topically "or" taken by mouth is thiabendazole (trade name "Mintezol")), an anti-helminthic.

- Topical freezing agents, such as ethylene chloride or liquid nitrogen, applied locally can freeze and kill the larvae, but this method has a high failure rate because the larvae are usually located away from the site of the visible skin trails. Additionally, this is a painful method which can cause blistering and/or ulceration of the skin and it is therefore not recommended.

- It is recommended to use Benadryl or some anti-itch cream (i.e. Cortizone or Calamine lotion). This will help relieve some of the itch.

- Wearing shoes in areas where these parasites are known to be endemic offers protection from infection. In general, avoiding exposure of skin to contaminated soil or sand offers the best protection. In some areas dogs have been banned from beaches in an attempt to control human infection.

Patient presents with the following signs.

1. Hyperkeratotic papules present over the seborrheic area of the body.

2. V - shaped nicking present at the tip of the nails.

3. Red and white longitudinal nail lines.

A dermatomycosis is a skin disease caused by a fungus. This excludes dermatophytosis.

Examples of dermatomycoses are tinea and cutaneous candidiasis.

Other rashes that occur in a widespread distribution can look like an id reaction. These include atopic dermatitis, contact dermatitis, dyshidrosis, photodermatitis, scabies and drug eruptions.

X-rays can be used to examine the lung tissue, however it can not be used to positively diagnose geotrichosis. X-rays may show cavitation that is located the walls of the lungs tissues. The lung tissue resemble the early signs of tuberculosis. The results of an x-ray examination of pulmonary geotrichosis presents smooth, dense patchy infiltrations and some cavities. Bronchial geotrichosis shows peribronchial thickening with fine mottling may be present on middle or basilar pulmonary fields. Bronchial geotrichosis usually present itself as non-specific diffuse peribronchical infiltration.

A 1992 study of 163 affected persons found that most patients had no other medical problems and most manage to lead a relatively normal life.

The infection causes a red, intensely pruritic (itchy) eruption. The itching can become very painful and if scratched may allow a secondary bacterial infection to develop. Cutaneous larva migrans usually heals spontaneously over weeks to months and has been known to last as long as one year. However, the severity of the symptoms usually causes those infected to seek medical treatment before spontaneous resolution occurs. Following proper treatment, migration of the larvae within the skin is halted and relief of the associated itching can occur in less than 48 hours (reported for thiabendazole).

This is separate from the similar cutaneous larva currens which is caused by "Strongyloides". Larva currens is also a cause of migratory pruritic eruptions but is marked by 1) migratory speed on the order of inches per hour 2) perianal involvement due to autoinfection from stool and 3) a wide band of urticaria.

Symptoms of vaginal candidiasis are also present in the more common bacterial vaginosis; aerobic vaginitis is distinct and should be excluded in the differential diagnosis. In a 2002 study, only 33% of women who were self-treating for a yeast infection actually had such an infection, while most had either bacterial vaginosis or a mixed-type infection.

Diagnosis of a yeast infection is done either via microscopic examination or culturing. For identification by light microscopy, a scraping or swab of the affected area is placed on a microscope slide. A single drop of 10% potassium hydroxide (KOH) solution is then added to the specimen. The KOH dissolves the skin cells, but leaves the "Candida" cells intact, permitting visualization of pseudohyphae and budding yeast cells typical of many "Candida" species.

For the culturing method, a sterile swab is rubbed on the infected skin surface. The swab is then streaked on a culture medium. The culture is incubated at 37 °C (98.6 °F) for several days, to allow development of yeast or bacterial colonies. The characteristics (such as morphology and colour) of the colonies may allow initial diagnosis of the organism causing disease symptoms.

Respiratory, gastrointestinal, and esophageal candidiasis require an endoscopy to diagnose. For gastrointestinal candidiasis, it is necessary to obtain a 3–5 milliliter sample of fluid from the duodenum for fungal culture. The diagnosis of gastrointestinal candidiasis is based upon the culture containing in excess of 1,000 colony-forming units per milliliter.

A boil may clear up on its own without bursting, but more often it will need to be opened and drained. This will usually happen spontaneously within two weeks. Regular application of a warm moist compress, both before and after a boil opens, can help speed healing. The area must be kept clean, hands washed after touching it, and any dressings disposed of carefully, in order to avoid spreading the bacteria. A doctor may cut open or "lance" a boil to allow it to drain, but squeezing or cutting should not be attempted at home, as this may further spread the infection. Antibiotic therapy may be recommended for large or recurrent boils or those that occur in sensitive areas (such as the groin, breasts, armpits, around or in the nostrils, or in the ear). Antibiotics should not be used for longer than one month, with at least two months (preferably longer) between uses, otherwise it will lose its effectiveness. If the patient has chronic (more than two years) boils, removal by plastic surgery may be indicated.

Furuncles at risk of leading to serious complications should be incised and drained if antibiotics or steroid injections are not effective. These include furuncles that are unusually large, last longer than two weeks, or occur in the middle of the face or near the spine. Fever and chills are signs of sepsis and indicate immediate treatment is needed.

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.