Diagnosis of oral candidal infection is made by identifying clinical features and ruling out other causes that may resemble oral candidiasis. Images of oral candidiasis can be found at www.dermnetnz.org.

• Pain is the main presenting symptom, and can make eating and drinking difficult.
• Loss or altered sense of taste may occur.
• Oral candidal infection may be asymptomatic.
• The clinical features vary according to the type of candidal infection:
• Pseudomembranous oral candidiasis (oral thrush):
• Presents with patches of curd-like white pseudomembrane on the cheeks, gums, and palate. These are easily removed, revealing an underlying red base that is not usually painful.
• Most commonly occurs in the first few weeks of life.
• Acute erythematous oral candidiasis (acute atrophic oral candidiasis):
• Presents with marked soreness and erythema, particularly on the dorsum of the tongue, and often follows on from oral thrush.
• Commonly occurs after treatment with oral antibiotics.
• Chronic erythematous oral candidiasis (denture stomatitis or chronic atrophic oral candidiasis):
• Presents with redness, and rarely soreness, in the denture-bearing area.
• Affects up to 50% of denture wearers.
• Chronic plaque-like oral candidiasis (chronic hyperplastic oral candidiasis):
• Presents with mild symptoms, with persistent firm, white plaques on the cheek or tongue, that are not easily removed.
• Is most common in men older than 30 years of age, and in smokers.
• Median rhomboid glossitis:
• Presents with a central, red, demarcated area of papillary atrophy of the tongue (from the posterior midline just anterior to the circumvallate papillae).
• Is usually seen in smokers or people using corticosteroid inhalers, and can lead to recurrent or chronic atrophic candidal infection.
• Angular cheilitis:
• Presents with redness, fissuring, and soreness at the angle of the mouth, and may be caused by bacterial infection (principally Staphylococcus aureus) as well as yeast (candida) species.
• Tends to occur in older people (particularly those with reduced facial height or with ill-fitting dentures), younger immunocompromised people, and people with vitamin B₁₂ deficiency or anaemia.
• Swabs to detect Candida albicans, or antibody serology, do not help to diagnose oral candidal infection because healthy people carry the organism.

[Hay and Moore, 2004; Gonsalves et al, 2007; Samaranayake et al, 2009]

• Oral candidiasis is only rarely confused with other oral conditions.
• Oral candidiasis is uncommon in people other than infants, denture wearers, and the elderly. Have an increased threshold for suspicion of other oral conditions in otherwise healthy individuals.
• In otherwise healthy people, candidiasis may be the first presentation of an undiagnosed risk factor, such as HIV infection, cancer, diabetes, anaemia, or haematinic deficiencies.
• Leukoplakia is defined as a white patch or plaque on the mucosa that cannot be rubbed off [Scully, 2004].
• It may be caused by chronic exposure to irritants (particularly tobacco), or chronic infection (particularly oral candidal infection).
• It is most commonly a benign condition, but may be premalignant.
• Biopsy of leukoplakia is required to distinguish benign lesions from premalignant lesions.
• Lichen planus is an inflammatory condition that affects 1–2% of adults, and is described as reticular or erosive.
• Reticular lichen planus is characterized by bilateral, asymptomatic, white, lacy, striations (or papules) on the posterior buccal mucosa. This form is easily identifiable and does not usually require further investigation.
• Erosive lichen planus manifests as zones of tender erythema and painful ulcers surrounded by white, radiating striae. It may require biopsy to rule out serious causes.
• Hairy tongue results from elongation of the filiform papillae on the dorsum of the tongue. It is associated with poor oral hygiene and overuse of mouthwashes.
• Erythema migrans (also known as geographic tongue or benign migratory glossitis) is an inflammatory disorder affecting 1–3% of the population, and is associated with atopic conditions and psoriasis. It is characterized by central erythema caused by atrophy of the filiform papillae, and surrounding (slightly elevated) white-yellow borders.

[Breathnach and Black, 2004; Scully, 2004; Gonsalves et al, 2007]