Redness occurs when the blood vessels in the white of the eye, sclera, expand. If the redness occurs in small localised areas, or spots, this is probably due to an injury. If the whole of the sclera appears reddened this may be caused by infection, allergy, glaucoma or simply tiredness.Treatment for the red eye depends on what caused it in the first place, thus if the redness does not quickly resolve or is marked, always consult your optician or general medical practitioner. If you wear contact lenses, and you suspect mild redness may be due to being in a smoky or dry environment, you can try comfort drops for immediate relief. If this does not work, or if the redness is marked, remove your lenses immediately and contact your optician.