Canker sores, medically termed aphthous ulcers, are common, painful lesions that appear as small, shallow wounds on the soft tissues inside the mouth. While uncomfortable and disruptive to eating or speaking, these ulcers are generally benign. They typically heal on their own within a couple of weeks. Understanding their characteristics helps alleviate anxiety about their cause and potential transmissibility.
Canker Sores are Not STDs
Canker sores are not sexually transmitted diseases (STDs). These lesions are non-contagious and cannot be passed through kissing, sharing utensils, or sexual contact. They result from a breakdown in the oral mucosal lining, not an infectious agent. Canker sores appear exclusively inside the mouth on movable, soft tissues like the tongue, cheeks, or soft palate. They present as a round or oval ulcer with a distinct white or yellowish center surrounded by a bright red, inflamed border.
Common Triggers and Etiology
While the exact cause remains unclear, canker sores result from a localized immune response triggered by non-infectious factors. Minor trauma is a frequent precursor, such as accidentally biting the cheek, aggressive brushing, or irritation from dental work. The damaged tissue becomes an entry point for an inflammatory reaction.
Fluctuations in the immune system also play a role, often leading to outbreaks during periods of emotional stress or hormonal changes. Recurrent cases are strongly linked to certain nutritional deficiencies. Low levels of B vitamins (B12 and folate), iron, and zinc can compromise the integrity of the oral mucosa and increase susceptibility to ulcer formation.
Dietary habits can also act as triggers, particularly the consumption of highly acidic or spicy foods. Items like citrus fruits, tomatoes, coffee, and certain cheeses can irritate the delicate lining of the mouth. Additionally, some people find that toothpastes containing the foaming agent sodium lauryl sulfate (SLS) may contribute to ulcer development.
Distinguishing Canker Sores from Cold Sores
Canker sores are often mistaken for cold sores (fever blisters), which are entirely different and highly contagious. The primary distinction lies in the cause: canker sores are non-viral, while cold sores are caused by the Herpes Simplex Virus (HSV), typically type 1. This viral origin makes cold sores transmissible through direct contact.
Location provides the clearest visual distinction. Canker sores occur only inside the mouth on soft tissue, while cold sores almost always appear outside the mouth, primarily on or around the lips. Their initial appearance is also dissimilar. Canker sores begin as a single, open ulcer with a white or yellow base. Cold sores emerge as a cluster of small, fluid-filled blisters that rupture, ooze, and then crust over. Because canker sores are non-viral and confined to the mouth’s interior, they pose no risk of transmission.
Management and Relief
Most minor canker sores heal naturally within one to two weeks, but simple measures can alleviate pain and accelerate healing. Rinsing the mouth with a solution of warm water and a teaspoon of salt or baking soda helps soothe the sore and promotes healing. Over-the-counter topical treatments containing mild anesthetics like benzocaine can be applied directly to the sore for temporary pain relief before eating or speaking. Avoiding known trigger foods, such as anything acidic, spicy, or abrasive, is important during the healing period to prevent further irritation. If a canker sore is unusually large, persists for longer than two weeks, or is accompanied by a high fever or difficulty swallowing, consult a healthcare professional.