What characterizes mouth ulcers, also known as canker sores?

Mouth ulcers, or canker sores, are characterized by lesions that occur on the mucous membranes within the oral cavity. These lesions are typically shallow, painful sores that can make eating, speaking, or even swallowing quite uncomfortable. They appear as whitish or yellowish sores surrounded by a red halo and are not caused by a viral or infectious process but may be associated with factors such as stress, hormonal changes, or certain food sensitivities.

The other options do not accurately describe the nature of canker sores. For instance, mouth ulcers are not located on the skin, nor do they form blisters. Additionally, while bacteria can inhabit the throat, the presence of canker sores is not directly related to bacterial growth in that area. Thus, the defining characteristic of mouth ulcers as lesions on the mucous membrane is what distinguishes them within the context of oral health.