Aphthous Ulcers: These are the most common cause of oral sores and can present as red bumps or ulcers in the mouth. They are often recurrent and can be triggered by stress, trauma, or certain foods.

Herpes Simplex Virus (HSV): HSV can cause oral sores, including cold sores and genital herpes. The presence of red bumps and oral sores, especially if they are painful and vesicular, could suggest an HSV infection.
Hand, Foot, and Mouth Disease: This is a common viral illness that can cause red bumps and oral sores, especially in children. It is usually caused by coxsackievirus A or enterovirus 71.
Allergic Contact Stomatitis: This is an allergic reaction that can cause red bumps and oral sores, often due to an allergic reaction to a food, toothpaste, or other substance.

Oral Cancer: Although less common, oral cancer can present as red bumps or oral sores that do not heal. It is essential to consider this diagnosis, especially in patients with a history of tobacco or alcohol use.
Lichen Planus: This is an autoimmune condition that can cause oral sores and red bumps. It can be associated with other systemic symptoms and can increase the risk of oral cancer.
Erythema Multiforme: This is a rare but serious condition that can cause oral sores and red bumps, often in response to an infection or medication.

Pemphigus Vulgaris: This is a rare autoimmune condition that can cause oral sores and red bumps, often with significant morbidity and mortality if left untreated.
Behçet's Disease: This is a rare condition that can cause oral sores and red bumps, often in combination with other systemic symptoms such as genital ulcers and eye inflammation.
Kawasaki Disease: This is a rare condition that can cause oral sores and red bumps, often in combination with other systemic symptoms such as fever, rash, and lymphadenopathy.