No preventive measure is known aside from avoiding the traumatic inoculation of fungi. At least one study found a correlation between walking barefoot in endemic areas and occurrence of chromoblastomycosis on the foot.

The prognosis for chromoblastomycosis is very good for small lesions. Severe cases are difficult to cure, although the prognosis is still quite good. The primary complications are ulceration, lymphedema, and secondary bacterial infection. A few cases of malignant transformation to squamous cell carcinoma have been reported. Chromoblastomycosis is very rarely fatal.

Buruli ulcer commonly affects poor people in remote rural areas with limited access to health care. The disease can affect all age groups, although children under the age of 15 years (range 2–14 years) are predominantly affected. There are no sex differences in the distribution of cases among children. Among adults, some studies have reported higher rates among women than males (Debacker "et al." accepted for publication). No racial or socio-economic group is exempt from the disease. Most ulcers occur on the extremities; lesions on the lower extremities are almost twice as common as those on the upper extremities. Ulcers on the head and trunk accounted for less than 8% of cases in one large series.

A recent retrospective study of all cases of Ecthyma gangrenosum from 2004-2010 in a university hospital in Mexico shows that neutropenia in immunocompromised patients is the most common risk factor for ecthyma gangrenosum.

While curable, BA is potentially fatal if not treated. BA responds dramatically to several antibiotics. Usually, erythromycin will cause the skin lesions to gradually fade away in the next four weeks, resulting in complete recovery. Doxycycline may also be used. However, if the infection does not respond to either of these, the medication is usually changed to tetracycline. If the infection is serious, then a bactericidal medication may be coupled with the antibiotics

If a cat is carrying "Bartonella henselae", then it may not exhibit any symptoms. Cats may be bacteremic for weeks to years, but infection is more common in young cats. Transmission to humans is thought to occur via flea feces inoculated into a cat scratch or bite, and transmission between cats occurs only in the presence of fleas. Therefore, elimination and control of fleas in the cat's environment are key to prevention of infection in both cats and humans.

It is caused by either "Bartonella henselae" or "B. quintana".

- "B. henselae" is most often transmitted through a cat scratch or bite, though ticks and fleas may also act as vectors.

- "B. quintana" is usually transmitted by lice.

It can manifest in people with AIDS and rarely appears in those who are immunocompetent.

Buruli ulcer has been reported from at least 32 countries around the world, mostly in tropical areas:

- West Africa: Benin, Burkina Faso, Côte d'Ivoire, Ghana, Liberia, Nigeria, Togo, Guinea, Sierra Leone.

- Other African Countries: Angola, Cameroon, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon, Sudan, Uganda.

- Western Pacific: Australia, Papua New Guinea, Kiribati.

- Americas: French Guiana, Mexico, Peru, Suriname.

- Asia: China, Malaysia, Japan.

In several of these countries, the disease is not considered to be a public health problem, hence the current distribution and the number of cases are not known. Possible reasons include:

- the distribution of the disease is often localized in certain parts of endemic countries;

- Buruli ulcer is not a notifiable disease

- In most places where the disease occurs, patients receive care from private sources such as voluntary mission hospitals and traditional healers. Hence the existence of the disease may not come to the attention of the ministries of health.

It most commonly occurs in Africa: Congo and Cameroon in Central Africa, Côte d'Ivoire, Ghana and Benin in West Africa. Some Southeast Asian countries (Papua New Guinea) and Australia have major foci, and there have been a few patients reported from South America (French Guyana and Surinam) and Mexico. Focal outbreaks have followed flooding, human migrations, and man-made topographic modifications such as dams and resorts. Deforestation and increased basic agricultural activities may significantly contribute to the recent marked increases in the incidence of "M. ulcerans" infections, especially in West Africa, where the disease is rapidly emerging.

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.

Cutaneous larva migrans (abbreviated CLM) is a skin disease in humans, caused by the larvae of various nematode parasites of the hookworm family (Ancylostomatidae). The most common species causing this disease in the Americas is "Ancylostoma braziliense". These parasites live in the intestines of dogs, cats, and wild animals and should not be confused with other members of the hookworm family for which humans are definitive hosts, namely "Ancylostoma duodenale" and "Necator americanus".

Colloquially called creeping eruption due to its presentation, the disease is also somewhat ambiguously known as "ground itch" or (in some parts of the Southern USA) "sandworms", as the larvae like to live in sandy soil. Another vernacular name is plumber's itch. The medical term CLM literally means "wandering larvae in the skin".

The organism enters directly through the breakdown of mechanical defense barriers such as mucosa or skin. Immunocompromised conditions make the patient more susceptible to this infection and septicemia. In case of septicemia, the bacteria reaches the skin via the bloodstream. Defective humoral or cellular immune system increases the risk because the organism is not able to be cleared from the bloodstream. The main mechanism of the organism that is causing the typical skin lesions is the invasion of the organism into the arteries and veins in the dermis and subcutaneous tissues of the skin. This perivascular invasion leads to nodular formation, ulceration, vasculitis and necrosis due to impaired blood supply. Perivascular involvement is achieved by direct entry of bacteria through the skin or hematogenous spreading in case of sepsis.

The horse should be kept in a clean, dry indoor barn stall with wood shavings for bedding to prevent a moist environment around the legs.

Preventative action should be taken as soon as the paddocks start to become wet and muddy. Rotation of paddocks keeps horses from having to stand in wet, muddy ground. Electric fencing may also prevent horses from standing for long periods in the deep mud that collects in high traffic areas.

The medieval "Bald's Leechbook" recommended treating chilblains with a mix of eggs, wine, and fennel root.

A common tradition of Hispanic America recommends warm garlic on the chilblains.

Sunscreen and protective clothing should also be used during the hottest part of the day to avoid blisters from sunburn. Avoiding sunlight during midday is the best way to avoid blisters from sunburn. Protective gloves should be worn when handling detergents, cleaning products, solvents and other chemicals.

An ameboma, also known as an amebic granuloma, is a rare complication of "Entamoeba histolytica" infection, where in response to the infecting amoeba there is formation of annular colonic granulation, which results in a large local lesion of the bowel.

Chilblains — also known as pernio, chill burns and perniosis — is a medical condition that occurs when a predisposed individual is exposed to cold and humidity, causing tissue damage. It is often confused with frostbite and trench foot. Damage to capillary beds in the skin causes redness, itching, inflammation, and sometimes blisters. Chilblains can be reduced by keeping the feet and hands warm in cold weather, and avoiding extreme temperature changes. Chilblains can be idiopathic (spontaneous and unrelated to another disease), but may also be a manifestation of another serious medical condition that must be investigated. A history of chilblains suggests a connective tissue disease (such as lupus). In infants, chilblains together with severe neurologic disease and unexplained fevers occurs in Aicardi–Goutières syndrome, a rare inherited condition.

Acroangiodermatitis of Mali (also known as "Mali acroangiodermatitis" and "Pseudo-Kaposi's sarcoma") is a rare cutaneous condition often characterized by purplish-blue to brown papules and plaques on the medial and lateral malleolus of both legs.

Acroangiodermatitis is a rare skin condition characterised by hyperplasia of pre-existing vasculature due to venous hypertension from severe chronic venous stasis. It is associated with amputees, haemodialysis (HD) patients with arteriovenous (AV) shunts, and patients with paralysed legs, hepatitis C, chronic venous insufficiency or AV malformations (AVM). Patients present with itchy, painful, confluent, violaceous or brown-black macules, papules or plaques usually at the distal lower limbs. There may be ulceration and bleeding. The histologic features are capillary proliferation and perivascular inflammation involving eosinophils in the dermis with minimal epidermal changes. Management includes compression therapy, wound care and surgical correction of AVM. Dapsone combined with leg elevation and compression, and erythromycin for HD patients with AV fistulas have also been reported. The lesions may persist for years with complications like ulceration, bleeding and infection.

Sometimes, the skin will blister when it comes into contact with a cosmetic, detergent, solvent, or other chemical such as nickel sulfate, Balsam of Peru, or urushiol (poison ivy, poison oak, poison sumac). This is known as contact dermatitis. Blisters can also develop as a result of an allergic reaction to an insect bite or sting. Some chemical warfare agents, known as blister agents or vesicants, cause large, painful blisters wherever they contact skin; an example is mustard gas.

Among those in the intensive care unit, ulceration resulting in bleeding is very rare.

Due to the difficulty of exploring host and amebic factors involved in the pathogenesis of amebic liver abscess in humans, most studies have been conducted with animal models (e.g., mice, gerbils, and hamsters). Histopathological findings revealed that the chronic phase of amebic liver abscess in humans corresponds to lytic or liquefactive necrosis, whereas in rodent models there is granulomatous inflammation. However, the use of animal models has provided important information on molecules and mechanisms of the host/parasite interaction in amebic liver abscess.

The ameboma may manifest as a right lower quadrant abdominal mass, which may be mistaken for carcinoma, tuberculosis, Crohn's disease, actinomycosis, or lymphoma.

AC is caused by chronic and excessive exposure to ultraviolet radiation in sunlight.

Risk factors include:

- Outdoor lifestyle: e.g. farmers, sailors, fishermen, windsurfers, mountaineers, golfers, etc. This has given rise to synonyms for this condition such as "sailor's lip" and "farmer's lip". The prevalence in agricultural workers in a semi-arid region of Brazil is reported to be 16.7%.

- Light skin complexion: the condition typically affects individuals with lighter skin tones, particularly Caucasians living in tropical regions. In one report, 96% of persons with AC had phenotype II according to the Fitzpatrick scale.

- Age: AC typically affects older individuals, and rarely those under the age of 45.

- Gender: the condition affects males more commonly than females. Sometimes this ratio is reported as high as 10:1.

Additional factors may also play a role, including tobacco use, lip irritation, poor oral hygiene, and ill-fitting dentures.

Many infections can cause oral ulceration (see table). The most common are herpes simplex virus (herpes labialis, primary herpetic gingivostomatitis), varicella zoster (chicken pox, shingles), and coxsackie A virus (hand, foot and mouth disease). Human immunodeficiency virus (HIV) creates immunodeficiencies which allow opportunistic infections or neoplasms to proliferate. Bacterial processes leading to ulceration can be caused by "Mycobacterium tuberculosis" (tuberculosis) and "Treponema pallidum" (syphilis).

Opportunistic activity by combinations of otherwise normal bacterial flora, such as aerobic streptococci, "Neisseria", "Actinomyces", spirochetes, and "Bacteroides" species can prolong the ulcerative process. Fungal causes include "Coccidioides immitis" (valley fever), "Cryptococcus neoformans" (cryptococcosis), and "Blastomyces dermatitidis" ("North American Blastomycosis"). Entamoeba histolytica, a parasitic protozoan, is sometimes known to cause mouth ulcers through formation of cysts.

To prevent AC from developing, protective measures could be undertaken such as avoiding mid-day sun, or use of a broad-brimmed hat, lip balm with anti UVA and UVB ingredients (e.g. para-aminobenzoic acid), or sun blocking agents (e.g. zinc oxide, titanium oxide) prior to sun exposure.

Many drugs can cause mouth ulcers as a side effect. Common examples are alendronate (a bisphosphonate, commonly prescribed for osteoporosis), cytotoxic drugs (e.g. methotrexate, i.e. chemotherapy), non-steroidal anti-inflammatory drugs, nicorandil (may be prescribed for angina) and propylthiouracil (e.g. used for hyperthyroidism). Some recreational drugs can cause ulceration, e.g. cocaine.