What is the difference between a cold sore and a canker sore?

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1. 1

   Aphthous stomatitis (Wikipedia)

   WikipediaPublished Oct 14, 2026Checked Oct 17, 2026

   “Aphthous stomatitis, or recurrent aphthous stomatitis (RAS), commonly referred to as a canker sore or salt blister, is a common condition characterized by the repeated formation of benign and non-contagious mouth ulcers (aphthae) in otherwise healthy individuals. The cause is not completely understood but involves a T cell-mediated immune response triggered by a variety of factors which may include nutritional deficiencies, local trauma, stress, hormonal influences, allergies, genetic predisposition, certain foods, dehydration, some food additives, or some hygienic chemical additives like SDS (common in toothpaste). These ulcers occur periodically and heal completely between attacks. In the majority of cases, the individual ulcers last about 7–10 days, and ulceration episodes occur 3–6 times per year. Most appear on the non-keratinizing epithelial surfaces in the mouth – i.e., anywhere except the attached gingiva, the hard palate, and the dorsum of the tongue. However, the more severe forms, which are less common, may also involve keratinizing epithelial surfaces. Symptoms range from a minor nuisance to interfering with eating and drinking.”

2. 2

   Striking Oral Manifestation of Primary Herpetic Gingivostomatitis: A Case Report and Review of Human Herpesvirus Infections.

   International medical case reports journal (Insyafiana & Nur'aeny)Published Sep 12, 2025Checked Oct 17, 2026

   “Intraoral examination showed multiple ulcers, measuring 5 mm on the left buccal mucosa, tongue, and gingiva accompanied by enlargement of the anterior gingiva and palatine rugae. The diagnosis was Primary Herpetic Gingivostomatitis, with herpangina considered as a differential diagnosis.Case managementTreatment included acyclovir tablets, nystatin suspension, multivitamins, petroleum jelly, and oral hygiene and dietary instructions. There was improvement in the vesicles on the lips and ulcers on the buccal mucosa, tongue, and gingiva within one week, though white plaque remained on the dorsum of the tongue.ConclusionCharacteristics of oral manifestations caused by HHV infection include symptoms of fever, vesicles, multiple ulcers measuring less than 1 cm, and gingival enlargement as the basis for establishing a diagnosis of Primary Herpetic Gingivostomatitis related to herpesvirus alpha infection, although ulcers also appear in herpesvirus beta and herpesvirus gamma but usually the ulcers will persist for more than two weeks with a relatively larger size, not accompanied by vesicles, and no gingival enlargement.”

3. 3

   Mouth ulcer (Wikipedia)

   WikipediaPublished Oct 14, 2026Checked Oct 17, 2026

   “A mouth ulcer (aphtha), or sometimes called a canker sore or salt blister, is an ulcer that occurs on the mucous membrane of the oral cavity. Mouth ulcers are very common, occurring in association with many diseases and by many different mechanisms, but usually there is no serious underlying cause. Rarely, a mouth ulcer that does not heal may be a sign of oral cancer. These ulcers may form individually or multiple ulcers may appear at once (i.e., a "crop" of ulcers). Once formed, an ulcer may be maintained by inflammation and/or secondary infection. The two most common causes of oral ulceration are local trauma (e.g. rubbing from a sharp edge on a broken filling or braces, biting one's lip, etc.) and aphthous stomatitis ("canker sores"), a condition characterized by the recurrent formation of oral ulcers for largely unknown reasons. Mouth ulcers often cause pain and discomfort and may alter the person's choice of food while healing occurs (e.g. avoiding acidic, sugary, salty or spicy foods and beverages).”

4. 4

   Diaspora of oral maxillofacial pathology and dermatopathology-A review.

   Bioinformation (Kandasamy et al.)Published May 31, 2026Checked Oct 17, 2026

   “Oral lesions may precede cutaneous or systemic manifestations in several conditions, including lichen planus, pemphigus vulgaris, viral infections, connective tissue disorders, vasculitic syndromes and immunodeficiency-associated diseases. The clinical appearance of oral lesions is often modified by salivation, mastication, microbial colonization, trauma and the thin nature of non-keratinized mucosa. Therefore, lesions that appear as vesicles or bullae on skin may present intraorally as erosions, ulcers, pseudomembranes, or erythematous areas. Recognition of these oral "sentinel" lesions is clinically important because early diagnosis can improve patient outcomes, guide systemic evaluation and facilitate timely referral. Thus, we review the clinicopathological basis of oral-cutaneous correlation and summarize important infectious, autoimmune, vesiculobullous, vasculitic, genetic, emergency, granulomatous and histiocytic disorders with oral manifestations. Hence, a multidisciplinary approach involving dentists, dermatologists, physicians and pathologists is essential for accurate diagnosis and comprehensive management.”

5. 5

   Orolabial Herpes Simplex Virus Type 2 Infection: A Case Report Highlighting the Importance of Viral Typing.

   Clinical case reports (Chu et al.)Published Aug 17, 2026Checked Oct 17, 2026

   “HSV-2 can present as atypical orolabial lesions and may be misdiagnosed as HSV-1. Viral typing is essential in atypical cases to ensure accurate diagnosis, appropriate management, and effective patient counseling.”