Red eye: causes, red flags and when to seek help

Before working out the cause, eye clinicians ask three things. Does it hurt, beyond a gritty or itchy feeling? Is your vision blurred, even slightly, and does it clear on blinking? Does bright light make it hurt? Yes to any of these means the problem may involve the cornea, the iris or the pressure inside the eye, not just the surface.

The NHS says that if your eye does not hurt, your sight is not affected and you do not feel sick or unwell, it is probably nothing serious and may get better by itself in a few days. Until then it suggests trying not to touch or rub the eye and not wearing contact lenses.

The NHS links a bright red area in the white of the eye with a burst blood vessel, a gritty or burning feeling with sticky eyes with conjunctivitis, sore, blurry or watery eyes with dry eyes, itchy, sore or red crusted eyelids with blepharitis, a feeling of something in the eye with an ingrowing eyelash, and a swollen, drooping or twitching eyelid or a lump on the eyelid with eyelid problems. It stresses not diagnosing yourself.

The NHS describes conjunctivitis as red or pink eye that usually affects both eyes and makes them red, burn or feel gritty, produce pus that sticks to lashes, itch and water. Conjunctivitis that produces sticky pus is contagious, while that caused by allergies such as hay fever makes eyes red and watery but is not contagious.

It advises washing the eyelids with cooled boiled water on clean cotton wool, a cold flannel for a few minutes, and no contact lenses until better. It says a pharmacist can suggest eyedrops or antihistamines, that antibiotics help only bacterial infection and will not work for viral or allergic causes, and that you do not need to stay away from work or school unless you feel very unwell. To avoid spreading it, wash hands regularly, wash pillowcases and face cloths in hot water, do not share towels or pillows and do not rub your eyes.

The NHS says to call 999 or go to A&E if you have a red eye and any changes to your sight, like wavy lines, flashing or loss of vision, if it hurts to look at light, if you have a severe headache and feel sick, if your eye or eyes are very dark red, if you have injured your eye or something is stuck in it such as glass or grit, if the injury was caused by a dangerous liquid such as a chemical, or if one pupil is bigger than the other.

It advises an urgent appointment with a GP or optician, or NHS 111, if your eye is very painful and red, if you wear contact lenses, or if your baby has red eyes and is less than 28 days old. The conjunctivitis page uses 30 days for a baby with red, sticky eyes. It also lists pain, sensitivity to light, vision changes and very red eyes as signs of a more serious eye problem.

The NHS rosacea page notes that in someone with rosacea, a painful, blurred, light-sensitive, red or gritty eye could be keratitis, which can be serious if not treated urgently.

An optometrist or doctor will ask about onset, one or both eyes, discharge, pain, contact lens use, injury, recent colds, allergies, and any history of arthritis, skin disease or previous eye problems. They check visual acuity first, then look at the lids and conjunctiva with a light, and an optometrist or ophthalmologist can examine the cornea and the front of the eye under a slit-lamp microscope, often using a dye to show surface damage, and measure eye pressure.

The NHS says that if the GP or optician cannot find the cause, they may refer you to an eye specialist (ophthalmologist) for tests.

Resist rubbing, remove contact lenses and stay out of them until the eye is comfortable and clear, keep towels and flannels separate, and wash your hands before and after touching your face. Artificial tears can soothe dry eyes, and a warm compress with gentle lid cleaning helps blepharitis. Ask a pharmacist before using any eyedrops, particularly those that promise to take out redness, since overuse can cause rebound redness.

If you are not improving in a few days, or in 7 days for suspected conjunctivitis as the NHS advises, see a GP or optician.