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White and red patches in the mouth: approach

  • Approach to a complaint

Some white patches rub off (thrush), most do not. Lasting white or red patches without a cause need a biopsy, because a few are precancerous.

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What it is

A white lesion looks white because of thickened keratin, a surface pseudomembrane or scarring; a red lesion is red because the epithelium is thin or the vessels are dilated or inflamed. The first question is whether it wipes off: pseudomembranous candidiasis does, leaving a red base. Non-wiping white lesions range from harmless frictional keratosis and linea alba to lichen planus, hairy leukoplakia and leukoplakia, a clinical term for a white patch that cannot be characterised as any other condition and carries a risk of cancer. Erythroplakia (a velvety red patch) carries the highest risk of dysplasia or carcinoma.

Red flags

  • Red or mixed red-white patches (erythroplakia, speckled leukoplakia) are the most worrying.
  • Induration, ulceration, bleeding or growth suggest carcinoma.
  • High-risk sites: lateral and ventral tongue, floor of mouth, soft palate.
  • Risk factors: tobacco, alcohol, areca nut, previous oral cancer, immunosuppression.
  • Hairy leukoplakia on the side of the tongue suggests HIV or another cause of immunosuppression.

Step-by-step approach

  1. Ask about duration, pain, tobacco, alcohol, areca nut, dentures, sharp teeth and HIV or transplant status.
  2. Try to wipe the lesion with gauze: if it comes off, think of candidiasis.
  3. Look for a cause at the site: a sharp tooth, a denture, cheek biting, a hot or chemical burn.
  4. Look for a pattern: lacy white lines on both cheeks (lichen planus), corrugated plaques on the lateral tongue (hairy leukoplakia).
  5. Remove any cause and review in two to three weeks; biopsy what persists.

Keys to the differential

  • Frictional keratosis disappears within weeks after the irritant is removed; leukoplakia does not.
  • Lichen planus is bilateral and symmetrical; leukoplakia is usually a single patch.
  • A white patch with an ulcer or a firm base is cancer until proven otherwise.

Next step / Initial management

  • Wipeable patch: treat as candidiasis and look for the cause (inhaled steroid, dentures, diabetes, antibiotics, immunosuppression).
  • Non-wipeable patch with a clear cause: remove the cause, review in two to three weeks.
  • Persistent patch, any erythroplakia, ulcer, induration or growth: refer for biopsy, urgently if features suggest cancer.
  • Hairy leukoplakia: offer an HIV test.

Test yourself

Think of the answer, then tap the question to see it.

What simple test separates pseudomembranous candidiasis from other white lesions?

Wiping with gauze: candidiasis comes off and leaves a red base.

Which oral patch carries the highest risk of dysplasia or cancer?

Erythroplakia, a red velvety patch.

What should hairy leukoplakia on the lateral tongue prompt?

An HIV test, because it signals immunosuppression and Epstein–Barr virus replication.

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Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.

Sources: Benign Chronic White Lesions of the Oral Mucosa (StatPearls Publishing (NCBI Bookshelf), 2024); Premalignant Lesions of the Oral Mucosa (StatPearls Publishing (NCBI Bookshelf), 2023); Oral Leukoplakia (StatPearls Publishing (NCBI Bookshelf), 2023); Hairy Leukoplakia (StatPearls Publishing (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.