A runny nose and sneezing without fever are usually due to a common cold or allergy. Taking vitamin C is fine, but high doses are not always necessary; once daily is usually enough. You can also try steam inhalation, warm fluids, and saline nasal drops for relief. If symptoms are due to an allergy, an antihistamine like Cetirizine may help. If it lasts more than a week or worsens, consult a doctor for proper evaluation.