Rashes on a baby's face can have various causes, including allergies, irritants, heat rash, or viral infections. To treat the rashes, keep the area clean and dry, avoid using harsh soaps or lotions, and apply a gentle moisturizer. If the rashes worsen or are accompanied by other symptoms like fever or difficulty breathing, consult a pediatrician immediately. Prevent future occurrences by avoiding triggers, such as allergens or irritants, keeping the baby cool and comfortable, and maintaining good hygiene practices.