The most common symptom of a fungal nail infection is the nail becoming thickened and discoloured: white, black, yellow or green. As the infection progresses the nail can become brittle, with pieces breaking off or coming away from the toe or finger completely. If left untreated, the skin underneath and around the nail can become inflamed and painful. There may also be white or yellow patches on the nailbed or scaly skin next to the nail, and a foul smell. There is usually no pain or other bodily symptoms, unless the disease is severe. People with onychomycosis may experience significant psychosocial problems due to the appearance of the nail, particularly when fingers – which are always visible – rather than toenails are affected.

Dermatophytids are fungus-free skin lesions that sometimes form as a result of a fungus infection in another part of the body. This could take the form of a rash or itch in an area of the body that is not infected with the fungus. Dermatophytids can be thought of as an allergic reaction to the fungus.

Onychomycosis, also known as tinea unguium, is a fungal infection of the nail. This condition may affect toenails or fingernails, but toenail infections are particularly common.

Treatment may be based on the signs. Treatment may be with the medication terbinafine.

It occurs in about 10 percent of the adult population. It is the most common disease of the nails and constitutes about half of all nail abnormalities.

The term is from Ancient Greek ὄνυξ "ónux" "nail", μύκης "múkēs" "fungus" and -ωσις "ōsis" "functional disease."

As the common name for this condition implies, it causes itching or a burning sensation in the groin area, thigh skin folds or anus. It may involve the inner thighs and genital areas, as well as extending back to the perineum and perianal areas.

Affected areas may appear red, tan, or brown, with flaking, rippling, peeling or cracking skin.

The acute infection begins with an area in the groin fold about a half-inch across, usually on both sides. The area may enlarge, and other sores may develop. The rash has sharply defined borders that may blister and ooze.

Tinea cruris does have similar symptoms to Inverse psoriasis.

The skin typically presents as red and hot. These infections can be painful.

Pus is usually present, along with gradual thickening and browning discoloration of the nail plate.

Candidal intertrigo is an infection of the skin by "Candida albicans", more specifically located between intertriginous folds of adjacent skin.

Candidal onychomycosis is an infection of the nail plate by fungus caused by "Candida". In one study "Candida parapsilosis" was the most common species; "Candida albicans" is also a common agent.

Signs and symptoms of candidiasis vary depending on the area affected. Most candidal infections result in minimal complications such as redness, itching, and discomfort, though complications may be severe or even fatal if left untreated in certain populations. In healthy (immunocompetent) persons, candidiasis is usually a localized infection of the skin, fingernails or toenails (onychomycosis), or mucosal membranes, including the oral cavity and pharynx (thrush), esophagus, and the genitalia (vagina, penis, etc.); less commonly in healthy individuals, the gastrointestinal tract, urinary tract, and respiratory tract are sites of candida infection.

In immunocompromised individuals, "Candida" infections in the esophagus occur more frequently than in healthy individuals and have a higher potential of becoming systemic, causing a much more serious condition, a fungemia called candidemia. Symptoms of esophageal candidiasis include difficulty swallowing, painful swallowing, abdominal pain, nausea, and vomiting.

Thrush is commonly seen in infants. It is not considered abnormal in infants unless it lasts longer than a few weeks.

Infection of the vagina or vulva may cause severe itching, burning, soreness, irritation, and a whitish or whitish-gray cottage cheese-like discharge. Symptoms of infection of the male genitalia (balanitis thrush) include red skin around the head of the penis, swelling, irritation, itchiness and soreness of the head of the penis, thick, lumpy discharge under the foreskin, unpleasant odour, difficulty retracting the foreskin (phimosis), and pain when passing urine or during sex.

Common symptoms of gastrointestinal candidiasis in healthy individuals are anal itching, belching, bloating, indigestion, nausea, diarrhea, gas, intestinal cramps, vomiting, and gastric ulcers. Perianal candidiasis can cause anal itching; the lesion can be erythematous, papular, or ulcerative in appearance, and it is not considered to be a sexually transmissible disease. Abnormal proliferation of the candida in the gut may lead to dysbiosis. While it is not yet clear, this alteration may be the source of symptoms generally described as the irritable bowel syndrome, and other gastrointestinal diseases.

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.

Tinea cruris, also known as crotch itch, crotch rot, Dhobi itch, eczema marginatum, gym itch, jock itch, jock rot, scrot rot and ringworm of the groin is a dermatophyte fungal infection of the groin region in any sex, though more often seen in males.

The symptoms of vaginal thrush include vulval itching, vulval soreness and irritation, pain or discomfort during sexual intercourse (superficial dyspareunia), pain or discomfort during urination (dysuria) and vaginal discharge, which is usually odourless. This can be thin and watery, or thick and white, like cottage cheese.

As well as the above symptoms of thrush, vulvovaginal inflammation can also be present. The signs of vulvovaginal inflammation include erythema (redness) of the vagina and vulva, vaginal fissuring (cracked skin), edema (swelling from a build-up of fluid), also in severe cases, satellite lesions (sores in the surrounding area). This is rare, but may indicate the presence of another fungal condition, or the herpes simplex virus (the virus that causes genital herpes).

Periungual warts are warts that cluster around the fingernail or toenail. They appear as thickened, fissured cauliflower-like skin around the nail plate. Periungual warts often cause loss of the cuticle and paronychia. Nail biting increases susceptibility to these warts.

Warts of this kind often cause damage to the nail either by lifting the nail from the skin or causing the nail to partially detach. If they extend under the nail, then the patient may suffer pain as a result. Sometimes periungual wart infections resemble the changes that are found in onychomycosis. In worst cases, if the infection causes injury or damage to the nail matrix, deformity in the nail may become permanent.

As with other wart types, a number of treatments are available, including laser therapy, cryotherapy, salicylic acid, and other topical treatments.

This refers to a group of rare syndromes characterized by chronic candidal lesions on the skin, in the mouth and on other mucous membranes (i.e., a secondary oral candidiasis). These include Localized chronic mucocutaneous candidiasis, diffuse mucocutaneous candidiasis (Candida granuloma), candidiasis–endocrinopathy syndrome and candidiasis thymoma syndrome. About 90% of people with chronic mucocutaneous candidiasis have candidiasis in the mouth.

This is an elliptical or rhomboid lesion in the center of the dorsal tongue, just anterior (in front) of the circumvallate papillae. The area is depapillated, reddened (or red and white) and rarely painful. There is frequently "Candida" species in the lesion, sometimes mixed with bacteria.

Candidiasis is a fungal infection due to any type of "Candida" (a type of yeast). When it affects the mouth, it is commonly called thrush. Signs and symptoms include white patches on the tongue or other areas of the mouth and throat. Other symptoms may include soreness and problems swallowing. When it affects the vagina, it is commonly called a yeast infection. Signs and symptoms include genital itching, burning, and sometimes a white "cottage cheese-like" discharge from the vagina. Less commonly the penis may be affected, resulting in itchiness. Very rarely, the infection may become invasive, spreading to other parts of the body. This may result in fevers along with other symptoms depending on the parts involved.

More than 20 types of "Candida" can cause infection with "Candida albicans" being the most common. Infections of the mouth are most common among children less than one month old, the elderly, and those with weak immune systems. Conditions that result in a weak immune system include HIV/AIDS, the medications used after organ transplantation, diabetes, and the use of corticosteroids. Other risks include dentures and following antibiotic therapy. Vaginal infections occur more commonly during pregnancy, in those with weak immune systems, and following antibiotic use. Risk factors for invasive candidiasis include being in an intensive care unit, following surgery, low birth weight infants, and those with weak immune systems.

Efforts to prevent infections of the mouth include the use of chlorhexidine mouth wash in those with poor immune function and washing out the mouth following the use of inhaled steroids. Little evidence supports probiotics for either prevention or treatment even among those with frequent vaginal infections. For infections of the mouth, treatment with topical clotrimazole or nystatin is usually effective. By mouth or intravenous fluconazole, itraconazole, or amphotericin B may be used if these do not work. A number of topical antifungal medications may be used for vaginal infections including clotrimazole. In those with widespread disease, an echinocandin such as caspofungin or micafungin is used. A number of weeks of intravenous amphotericin B may be used as an alternative. In certain groups at very high risk, antifungal medications may be used preventatively.

Infections of the mouth occur in about 6% of babies less than a month old. About 20% of those receiving chemotherapy for cancer and 20% of those with AIDS also develop the disease. About three-quarters of women have at least one yeast infection at some time during their lives. Widespread disease is rare except in those who have risk factors.

Infections on the body may give rise to typical enlarging raised red rings of ringworm. Infection on the skin of the feet may cause athlete's foot and in the groin, jock itch. Involvement of the nails is termed onychomycosis, and they may thicken, discolour, and finally crumble and fall off. They are common in most adult people, with up to 20% of the population having one of these infections at any given moment.

Animals such as dogs and cats can also be affected by ringworm, and the disease can be transmitted between animals and humans, making it a zoonotic disease.

Specific signs can be:

- red, scaly, itchy or raised patches

- patches may be redder on outside edges or resemble a ring

- patches that begin to ooze or develop blister

- bald patches may develop, when the scalp is affected

- nails may thicken, discolour or begin to crack

Athlete's foot is divided into four categories or presentations: chronic interdigital athlete's foot, plantar (chronic scaly) athlete's foot (aka "moccasin foot"), acute ulcerative tinea pedis, and vesiculobullous athlete's foot. "Interdigital" means between the toes. "Plantar" here refers to the sole of the foot. The ulcerative condition includes macerated lesions with scaly borders. Maceration is the softening and breaking down of skin due to extensive exposure to moisture. A vesiculobullous disease is a type of mucocutaneous disease characterized by vesicles and bullae (blisters). Both vesicles and bullae are fluid-filled lesions, and they are distinguished by size (vesicles being less than 5–10 mm and bulla being larger than 5–10 mm, depending upon what definition is used).

Athlete's foot occurs most often between the toes (interdigital), with the space between the fourth and fifth digits most commonly afflicted. Cases of interdigital athlete's foot caused by "Trichophyton rubrum" may be symptomless, it may itch, or the skin between the toes may appear red or ulcerative (scaly, flaky, with soft and white if skin has been kept wet), with or without itching. An acute ulcerative variant of interdigital athlete's foot caused by "T. mentagrophytes" is characterized by pain, maceration of the skin, erosions and fissuring of the skin, crusting, and an odor due to secondary bacterial infection.

Plantar athlete's foot (moccasin foot) is also caused by "T. rubrum" which typically causes asymptomatic, slightly erythematous plaques (areas of redness of the skin) to form on the plantar surface (sole) of the foot that are often covered by fine, powdery hyperkeratotic scales.

The vesiculobullous type of athlete's foot is less common and is usually caused by "T. mentagrophytes" and is characterized by a sudden outbreak of itchy blisters and vesicles on an erythematous base, usually appearing on the sole of the foot. This subtype of athlete's foot is often complicated by secondary bacterial infection by "Streptococcus pyogenes" or "Staphylococcus aureus".

Bacterial intertrigo can be caused by "Streptococci" and "Corynebacterium minutissimum".

Uncomplicated thrush is when there are less than four episodes in a year, the symptoms are mild or moderate, it is likely caused by "Candida albicans", and there are no significant host factors such as poor immune function.

Intertrigo refers to a type of inflammatory rash (dermatitis) of the superficial skin that occurs within a person's body folds. These areas are more susceptible to irritation and subsequent infection due to factors that promote skin breakdown such as moisture, friction, and exposure to bodily secretions such as sweat, urine or feces. Areas of the body which are more likely to be affected by intertrigo include the inframammary fold, intergluteal cleft, armpits, and spaces between the fingers or toes. Skin affected by intertrigo is more prone to infection than intact skin.

The term "intertrigo" commonly refers to a secondary infection with bacteria (such as "Corynebacterium minutissimum"), fungi (such as "Candida albicans"), or viruses. A frequent manifestation is candidal intertrigo.

Intertrigo occurs more often in warm and humid conditions. Generally, intertrigo is more common in people with a weakened immune system including children, the elderly, and immunocompromised people. The condition is also more common in people who experience urinary incontinence and decreased ability to move.

The most common term for the infection, "ringworm", is a misnomer, since the condition is caused by fungi of several different species and not by parasitic worms.

As the disease progresses, the skin may crack, leading to bacterial skin infection and inflammation of the lymphatic vessels. If allowed to grow for too long, athlete's foot fungus may spread to infect the toenails, feeding on the keratin in them, a condition called onychomycosis.

Because athlete's foot may itch, it may also elicit the scratch reflex, causing the host to scratch the infected area before he or she realizes it. Scratching can further damage the skin and worsen the condition by allowing the fungus to more easily spread and thrive. The itching sensation associated with athlete's foot can be so severe that it may cause hosts to scratch vigorously enough to inflict excoriations (open wounds), which are susceptible to bacterial infection. Further scratching may remove scabs, inhibiting the healing process.

Scratching infected areas may also spread the fungus to the fingers and under the fingernails. If not washed away soon enough, it can infect the fingers and fingernails, growing in the skin and in the nails (not just underneath). After scratching, it can be spread to wherever the person touches, including other parts of the body and to one's environment. Scratching also causes infected skin scales to fall off into one's environment, leading to further possible spread.

When athlete's foot fungus or infested skin particles spread to one's environment (such as to clothes, shoes, bathroom, etc.) whether through scratching, falling, or rubbing off, not only can they infect other people, they can also reinfect (or further infect) the host they came from. For example, infected feet infest one's socks and shoes which further expose the feet to the fungus and its spores when worn again.

The ease with which the fungus spreads to other areas of the body (on one's fingers) poses another complication. When the fungus is spread to other parts of the body, it can easily be spread back to the feet after the feet have been treated. And because the condition is called something else in each place it takes hold (e.g., tinea corporis (ringworm) or tinea cruris (jock itch), persons infected may not be aware it is the same disease.

Some individuals may experience an allergic response to the fungus called an id reaction in which blisters or vesicles can appear in areas such as the hands, chest, and arms. Treatment of the underlying infection typically results in the disappearance of the id reaction.

In the context of lesions of the mucous membrane lining of the bladder, leukoplakia is a historic term used to describe a visualized white patch which histologically represents keratinization in an area of squamous metaplasia. The symptoms may include frequency, suprapubic pain (pain felt above the pubis), hematuria (blood in the urine), dysuria (difficult urination or pain during urination), urgency, and urge incontinence. The white lesion may be seen during cystoscopy, where it appears as a whitish-gray or yellow lesion, on a background of inflamed urothelium and there may be floating debris in the bladder. Leukoplakia of the bladder may undergo cancerous changes, so biopsy and long term follow up are usually indicated.

Most cases of leukoplakia cause no symptoms, but infrequently there may be discomfort or pain. The exact appearance of the lesion is variable. Leukoplakia may be white, whitish yellow or grey. The size can range from a small area to much larger lesions. The most common sites affected are the buccal mucosa, the labial mucosa and the alveolar mucosa, although any mucosal surface in the mouth may be involved. The clinical appearance, including the surface texture and color, may be homogenous or non-homogenous (see: classification). Some signs are generally associated with a higher risk of cancerous changes (see: prognosis).

Leukoplakia may rarely be associated with esophageal carcinoma.

Angular cheilitis is a fairly non specific term which describes the presence of an inflammatory lesion in a particular anatomic site (i.e. the corner of the mouth). As there are different possible causes and contributing factors from one person to the next, the appearance of the lesion is somewhat variable. The lesions are more commonly symmetrically present on both sides of the mouth, but sometimes only one side may be affected. In some cases, the lesion may be confined to the mucosa of the lips, and in other cases the lesion may extend past the vermilion border (the edge where the lining on the lips becomes the skin on the face) onto the facial skin. Initially, the corners of the mouth develop a gray-white thickening and adjacent erythema (redness). Later, the usual appearance is a roughly triangular area of erythema, edema (swelling) and breakdown of skin at either corner of the mouth. The mucosa of the lip may become fissured (cracked), crusted, ulcerated or atrophied. There is not usually any bleeding. Where the skin is involved, there may be radiating rhagades (linear fissures) from the corner of the mouth. Infrequently, the dermatitis (which may resemble eczema) can extend from the corner of the mouth to the skin of the cheek or chin. If "Staphylococcus aureus" is involved, the lesion may show golden yellow crusts. In chronic angular cheilitis, there may be suppuration (pus formation), exfoliation (scaling) and formation of granulation tissue.

Sometimes contributing factors can be readily seen, such as loss of lower face height from poorly made or worn dentures, which results in mandibular overclosure ("collapse of jaws"). If there is a nutritional deficiency underlying the condition, various other signs and symptoms such as glossitis (swollen tongue) may be present. In people with angular cheilitis who wear dentures, often there may be erythematous mucosa underneath the denture (normally the upper denture), an appearance consistent with denture-related stomatitis. Typically the lesions give symptoms of soreness, pain, pruritus (itching) or burning or a raw feeling.

Cheilitis is inflammation of the lips. This inflammation may include the perioral skin (the skin around the mouth), the vermilion border, and/or the labial mucosa. The skin and the vermilion border are more commonly involved, as the mucosa is less affected by inflammatory and allergic reactions.

It is a general term, and there are many recognized types and different causes. Cheilitis can be either acute or chronic. Most cheilitis is caused by exogenous factors such as dryness (chapping) and acute sun exposure. Patch testing may identify allergens that cause cheilitis.