Chancroid is a bacterial infection caused by the fastidious Gram-negative streptobacillus "Haemophilus ducreyi". It is a disease found primarily in developing countries, most prevalent in low socioeconomic groups, associated with commercial sex workers. In the United States socioeconomic status has not been found to be a factor in the spread of sexually transmitted diseases.

Chancroid, caused by H. ducreyi has infrequently been associated with cases of Genital Ulcer Disease in the US, but has been isolated in up to 10% of genital ulcers diagnosed from STD clinics in Memphis and Chicago.

Infection levels are very low in the Western world, typically around one case per two million of the population (Canada, France, Australia, UK and US). Most individuals diagnosed with chancroid have visited countries or areas where the disease is known to occur frequently, although outbreaks have been observed in association with crack cocaine use and prostitution.

Chancroid is a risk factor for contracting HIV, due to their ecological association or shared risk of exposure, and biologically facilitated transmission of one infection by the other.

A genital ulcer is located on the genital area, usually caused by a sexually transmitted disease such as genital herpes, syphilis, chancroid, or "Chlamydia trachomatis". Some other signs of having genital ulcers include enlarged lymph nodes in the groin area, or vesicular lesions, which are small, elevated sores or blisters. The syndrome may be further classified into penile ulceration and vulval ulceration for males and females respectively.

Genital ulcers are not strictly a sign of an STD. They can occur in patients with Behcet's syndrome, lupus, and some forms of rheumatoid arthritis (all non-communicable diseases). Genital tuberculosis, often caused by direct genital contact with infected sputum, can also present as genital ulcer.

All sores involve a breakdown in the walls of the fine membrane of the vaginal wall. The most common of these are abrasions and small ulcers caused by trauma. While these can be inflicted during rape most are actually caused by excessive rubbing from clothing or improper insertion of a sanitary tampon. The typical ulcer or sore caused by syphilis is painless with raised edges. These are often undetected because they occur mostly inside the vagina. The sores of herpes which occur with vesicles are extremely tender and may cause such swelling that passing urine is difficult. In the developing world, a group of parasitic diseases also cause vaginal ulceration, such as leishmaniasis, but these are rarely encountered in the west. All of the aforementioned local vulvovaginal diseases are easily treated. Often, only shame prevents patients from presenting for treatment.

Most vaginal discharges occur due to normal bodily functions, such as menstruation or sexual arousal (vaginal lubrication). Abnormal discharges, however, can indicate disease. Normal vaginal discharges include blood or menses (from the uterus), the most common, and clear fluid either as a result of sexual arousal or secretions from the cervix. Other non-infective causes include dermatitis. Non-sexually transmitted discharges occur from bacterial vaginosis, aerobic vaginitis and thrush or candidiasis. The final group of discharges include the sexually transmitted diseases gonorrhea, chlamydia, and trichomoniasis. The discharge from thrush is slightly pungent and white, that from trichomoniasis more foul and greenish, and that from foreign bodies resembling the discharge of gonorrhea, greyish or yellow and purulent (pus-like).

"H. ducreyi" enters skin through microabrasions incurred during sexual intercourse. A local tissue reaction leads to development of erythomatous papule, which progresses to pustule in 4–7 days. It then undergoes central necrosis to ulcerate.

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.

The thickness of the mucosa may be an important factor in aphthous stomatitis. Usually, ulcers form on the thinner, non-keratinizing mucosal surfaces in the mouth. Factors which decrease the thickness of mucosa increase the frequency of occurrence, and factors which increase the thickness of the mucosa correlate with decreased ulceration.

The nutritional deficiencies associated with aphthous stomatitis (B12, folate, and iron) can all cause a decrease in the thickness of the oral mucosa (atrophy).

Local trauma is also associated with aphthous stomatitis, and it is known that trauma can decrease the mucosal barrier. Trauma could occur during injections of local anesthetic in the mouth, or otherwise during dental treatments, frictional trauma from a sharp surface in the mouth such as broken tooth, or from tooth brushing.

Hormonal factors are capable of altering the mucosal barrier. In one study, a small group of females with apthous stomatitis had fewer occurrences of aphthous ulcers during the luteal phase of the menstrual cycle or with use of the contraceptive pill. This phase is associated with a fall in progestogen levels, mucosal proliferation and keratinization. This subgroup often experiences remission during pregnancy. However, other studies report no correlation between aphthous stomatitis and menstrual period, pregnancy or menopause.

Aphthous stomatitis is common in people who smoke, and there is also a correlation between habit duration and severity of the condition. Tobacco use is associated with an increase in keratinization of the oral mucosa. In extreme forms, this may manifest as leukoplakia or stomatitis nicotina (smoker's keratosis). This increased keratinization may mechanically reinforce the mucosa and reduce the tendency of ulcers to form after minor trauma, or present a more substantial barrier to microbes and antigens, but this is unclear. Nicotine is also known to stimulate production of adrenal steroids and reduce production of TNF-α, interleukin-1 and interleukin-6. Smokeless tobacco products also seem to protect against aphthous stomatitis. Cessation of smoking is known to sometimes precede the onset of aphthous stomatitis in people previously unaffected, or exacerbate the condition in those who were already experiencing aphthous ulceration. Despite this correlation, starting smoking again does not usually lessen the condition.

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.

Various antigenic triggers have been implicated as a trigger, including L forms of streptococci, herpes simplex virus, varicella-zoster virus, adenovirus, and cytomegalovirus. Some people with aphthous stomatitis may show herpes virus within the epithelium of the mucosa, but without any productive infection. In some persons, attacks of ulceration occur at the same time as asymptomatic viral shedding and elevated viral titres.

In some instances, recurrent mouth ulcers may be a manifestation of an allergic reaction. Possible allergens include certain foods ("e.g.", chocolate, coffee, strawberries, eggs, nuts, tomatoes, cheese, citrus fruits, benzoates, cinnamaldehyde, and highly acidic foods), toothpastes, and mouthwashes. Where dietary allergens are responsible, mouth ulcers usually develop within about 12–24 hours of exposure.

Sodium lauryl sulphate (SLS), a detergent present in some brands of toothpaste and other oral healthcare products, may produce oral ulceration in some individuals. It has been shown that aphthous stomatitis is more common in people using toothpastes containing SLS, and that some reduction in ulceration occurs when a SLS-free toothpaste is used. Some have argued that since SLS is almost ubiquitously used in oral hygiene products, there is unlikely to be a true predisposition for aphthous stomatitis caused by SLS.

The disorder typically appears among young girls and adolescents but cases in children as young as 17 months have been reported.

The wounds from which ulcers arise can be caused by a wide variety of factors, but the main cause is impaired blood circulation. Especially, chronic wounds and ulcers are caused by poor circulation, either through cardiovascular issues or external pressure from a bed or a wheelchair. A very common and dangerous type of skin ulcers are caused by what are called pressure-sensitive sores, more commonly called bed sores and which are frequent in people who are bedridden or who use wheelchairs for long periods. Other causes producing skin ulcers include bacterial or viral infections, fungal infections and cancers. Blood disorders and chronic wounds can result in skin ulcers as well.

Venous leg ulcers due to impaired circulation or a blood flow disorder are more common in the elderly.

Genital HPV infections have an estimated prevalence in the US of 10–20% and clinical manifestations in 1% of the sexually active adult population. US incidence of HPV infection has increased between 1975 and 2006. About 80% of those infected are between the ages of 17–33. Although treatments can remove the warts, they do not remove the HPV, so warts can recur after treatment (about 50–73% of the time). Warts can also spontaneously regress (with or without treatment).

Traditional theories postulated that the virus remained in the body for a lifetime. However, studies using sensitive DNA techniques have shown that through immunological response the virus can either be cleared or suppressed to levels below what polymerase chain reaction (PCR) tests can measure. One study testing genital skin for subclinical HPV using PCR found a prevalence of 10%.

HPV is most commonly transmitted through penetrative sex. While HPV can also be transmitted via non-penetrative sexual activity, it is less transmissible than via penetrative sex. There is conflicting evidence about the effect of condoms on transmission of low-risk HPV. Some studies have suggested that they are effective at reducing transmission. Other studies suggest that condoms are not effective at preventing transmission of the low-risk HPV variants that cause genital warts. The effect of condoms on HPV transmission may also be gender-dependent; there is some evidence that condoms are more effective at preventing infection of males than of females.

The types of HPV that cause warts are highly transmissible. Roughly three out of four unaffected partners of patients with warts develop them within eight months. Other studies of partner concordance suggest that the presence of visible warts may be an indicator of increased infectivity; HPV concordance rates are higher in couples where one partner has visible warts.

An ulcer is a sore on the skin or a mucous membrane, accompanied by the disintegration of tissue. Ulcers can result in complete loss of the epidermis and often portions of the dermis and even subcutaneous fat. Ulcers are most common on the skin of the lower extremities and in the gastrointestinal tract. An ulcer that appears on the skin is often visible as an inflamed tissue with an area of reddened skin. A skin ulcer is often visible in the event of exposure to heat or cold, irritation, or a problem with blood circulation. They can also be caused due to a lack of mobility, which causes prolonged pressure on the tissues. This stress in the blood circulation is transformed to a skin ulcer, commonly known as bedsores or decubitus ulcers. Ulcers often become infected, and pus forms.

Lipschütz ulcer, ulcus vulvae acutum or reactive non-sexually related acute genital ulcers () is a rare disease characterized by painful genital ulcers, fever, and lymphadenopathy, occurring most commonly, but not exclusively, in adolescents and young women. Previously, it was described as being more common in virgins. It is not a sexually transmitted disease, and is often misdiagnosed, sometimes as a symptom of Behçet's disease.

Lipschütz ulcer is named after Benjamin Lipschütz, who first described it in 1912. The cause is still unknown, although it has been associated with several infectious causes, including paratyphoid fever, cytomegalovirus, "Mycoplasma pneumoniae" and Epstein-Barr virus infection

There are over 100 risk factors for pressure ulcers. Factors that may place a patient at risk include immobility, diabetes mellitus, peripheral vascular disease, malnutrition, cerebral vascular accident and hypotension. Other factors are age of 70 years and older, current smoking history, dry skin, low body mass index, urinary and fecal incontinence, physical restraints, malignancy, and history of pressure ulcers.

Pressure ulcers can trigger other ailments, cause considerable suffering, and can be expensive to treat. Some complications include autonomic dysreflexia, bladder distension, bone infection, pyarthroses, sepsis, amyloidosis, anemia, urethral fistula, gangrene and very rarely malignant transformation (Marjolin's ulcer - secondary carcinomas in chronic wounds). Sores may recur if those with pressure ulcers do not follow recommended treatment or may instead develop seromas, hematomas, infections, or wound dehiscence. Paralyzed individuals are the most likely to have pressure sores recur. In some cases, complications from pressure sores can be life-threatening. The most common causes of fatality stem from kidney failure and amyloidosis.

Pressure ulcers are also painful, with individuals of all ages and all stages of pressure ulcers reporting pain.

Gardasil 6 is an HPV vaccine aimed at preventing cervical cancers and genital warts. Gardasil is designed to prevent infection with HPV types 16, 18, 6, and 11. HPV types 16 and 18 currently cause about 70% of cervical cancer cases, and also cause some vulvar, vaginal, penile and anal cancers. HPV types 6 and 11 are responsible for 90% of documented cases of genital warts.

Gardasil 9, approved in 2014 protects against HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58.

HPV vaccines do not currently protect against the virus strains responsible for plantar warts (verrucas).

Prognosis is highly variable. Spontaneous remission is common. Complete cure can be obtained with proper antibiotic treatments to kill the causative bacteria, such as tetracycline, doxycycline, or erythromycin. Prognosis is more favorable with early treatment. Bacterial superinfections may complicate course. Death can occur from bowel obstruction or perforation, and follicular conjunctivitis due to autoinoculation of infectious discharge can occur.

Corneal ulcer, or ulcerative keratitis, is an inflammatory or more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong. In ophthalmology, a corneal ulcer usually refers to having an infectious cause while the term corneal abrasion refers more to physical abrasions.

Tuberculosis cutis orificialis (also known as "acute tuberculous ulcer" and "orificial tuberculosis") is a form of cutaneous tuberculosis that occurs at the mucocutaneous borders of the nose, mouth, anus, urinary meatus, and vagina, and on the mucous membrane of the mouth or tongue.

Genital elephantiasis or esthiomene, which is the dramatic end-result of lymphatic obstruction, which may occur because of the strictures themselves, or fistulas. This is usually seen in females, may ulcerate and often occurs 1–20 years after primary infection.

Fistulas of, but not limited to, the penis, urethra, vagina, uterus, or rectum. Also, surrounding edema often occurs. Rectal or other strictures and scarring. Systemic spread may occur, possible results are arthritis, pneumonitis, hepatitis, or perihepatitis.

There is now considerable evidence to suggest that this disease is an infection. "Mycobacterium ulcerans" has recently been isolated from lesions and is unique to tropical ulcers. Early lesions may be colonized or infected by, "Bacillus fusiformis" (Vincent's organism), anaerobes and spirochaetes. Later, tropical ulcer may become infected with a variety of organisms, notably, staphylococci and/or streptococci. The condition has been shown to be transmissible by inoculation of material from affected patients.

Adequate footwear is important to prevent trauma. General good health and nutrition also reduce ulcer risk. Adequate and prompt cleansing and treatment of ankle and leg skin breaks is also important. Improving hygiene and nutrition may help to prevent tropical ulcers.

Corneal ulcers are a common human eye disease. They are caused by trauma, particularly with vegetable matter, as well as chemical injury, contact lenses and infections. Other eye conditions can cause corneal ulcers, such as entropion, distichiasis, corneal dystrophy, and keratoconjunctivitis sicca (dry eye).

Many micro-organisms cause infective corneal ulcer. Among them are bacteria, fungi, viruses, protozoa, and chlamydia:

- Bacterial keratitis is caused by "Staphylococcus aureus", "Streptococcus viridans", "Escherichia coli", "Enterococci", "Pseudomonas", "Nocardia", "N. Gonorrhoea" and many other bacteria.

- Fungal keratitis causes deep and severe corneal ulcer. It is caused by "Aspergillus" sp., "Fusarium" sp., "Candida" sp., as also "Rhizopus", "Mucor", and other fungi. The typical feature of fungal keratitis is slow onset and gradual progression, where signs are much more than the symptoms. Small satellite lesions around the ulcer are a common feature of fungal keratitis and hypopyon is usually seen.

- Viral keratitis causes corneal ulceration. It is caused most commonly by Herpes simplex, Herpes zoster and Adenoviruses. Also it can be caused by coronaviruses & many other viruses. Herpes virus cause a dendritic ulcer, which can recur and relapse over the lifetime of an individual.

- Protozoa infection like "Acanthamoeba keratitis" is characterized by severe pain and is associated with contact lens users swimming in pools.

- "Chlamydia trachomatis" can also contribute to development of corneal ulcer.

Superficial ulcers involve a loss of part of the epithelium. Deep ulcers extend into or through the stroma and can result in severe scarring and corneal perforation. Descemetoceles occur when the ulcer extends through the stroma. This type of ulcer is especially dangerous and can rapidly result in corneal perforation, if not treated in time.

The location of the ulcer depends somewhat on the cause. Central ulcers are typically caused by trauma, dry eye, or exposure from facial nerve paralysis or exophthalmos. Entropion, severe dry eye and trichiasis (inturning of eyelashes) may cause ulceration of the peripheral cornea. Immune-mediated eye disease can cause ulcers at the border of the cornea and sclera. These include Rheumatoid arthritis, rosacea, systemic sclerosis which lead to a special type of corneal ulcer called Mooren's ulcer. It has a circumferential crater like depression of the cornea, just inside the limbus, usually with an overhanging edge.