Recurrent mouth ulcers often happen due to underlying causes like vitamin deficiencies (especially B12, iron), stress, hormonal changes, or minor immune issues. Instead of only treating each episode, a long-term fix is to correct the cause, she can take a B-complex supplement, maintain good oral hygiene, avoid very spicy or acidic foods, and manage stress. If ulcers keep returning, a doctor may check for deficiencies or prescribe preventive treatment like Kenacort oral paste or other medicines for longer control.