Eye drops from the pharmacy: which are safe for a red eye, and why whitening and steroid drops are a problem

A red eye is the most common reason people walk to the pharmacy shelf of eye drops, and the shelf is a mixed bag. Some bottles are harmless, some hide a problem, and one kind, the steroid drop, can damage an eye that looked merely irritated. This article sorts them by what they do, so you can tell which are safe to try and which should wait for a doctor.

What can I safely put in a red eye from the pharmacy?

For a mildly red, gritty or tired eye with no pain and normal vision, plain lubricating drops, sold as artificial tears, are the safe first choice. For a red eye that itches, an antihistamine drop is reasonable. Whitening drops and steroid drops are the two to avoid unless a doctor has told you to use them.

The NHS advice for conjunctivitis, which is inflammation of the conjunctiva, the thin clear membrane over the white of the eye, is to speak to a pharmacist, who can suggest eyedrops or antihistamines for symptoms. The NHS also advises holding a cold flannel over the eyes and stopping contact lenses until the eyes improve. The American Academy of Ophthalmology adds that placing a cool, wet washcloth on the eyes and lubricating them with artificial tears can make them more comfortable, and that conjunctivitis usually goes away on its own within one to two weeks.

The useful habit is to ask what the redness is. A 2026 interview study of 18 ophthalmologists found dry eye disease to be the most commonly cited underlying cause of ocular redness. Redness is a sign, not a diagnosis. A drop that only removes the sign leaves the cause where it was. Why a dry surface goes red is in my article on dry eyes after fifty.

Should I choose preservative-free or preserved lubricating drops?

Preservative-free is the better choice if you will use drops often, and the American Academy of Ophthalmology sets the line at more than six times a day. A preserved bottle is acceptable for occasional use. The preservative is there to keep a multi-dose bottle clean, and it can irritate an eye that is already sore.

The Academy's wording is specific. It says you can use artificial tears as often as you need to, that if you use them more than six times a day or are allergic to preservatives you should use preservative-free tears, and that tears with preservatives may start to irritate your eyes.

One practical point. If you need lubricant every day for weeks, the drop is not the answer on its own. Dry eye that persists is usually a lid margin or a tear film problem, and that deserves an examination. Lubricating drops are also what I would use for the surface after eyelid surgery, which I cover in the page on dry eye after eyelid surgery.

Why do whitening eye drops make the eye redder in the end?

Because they work by squeezing the small blood vessels on the white of the eye, and the vessels tend to swell back wider once the effect wears off. The medical terms are tachyphylaxis, meaning the drop works less well each time, and rebound redness, meaning the eye returns redder than before.

These are decongestant or vasoconstrictor drops, and the active ingredients are alpha-adrenergic agonists, a class of medicine that tightens blood vessels. A 2026 narrative review in Ophthalmology and Therapy states that ocular decongestants give effective short-term relief, but that the older alpha-1 and mixed alpha-1 and alpha-2 agents are associated with tachyphylaxis and rebound redness. A second 2026 study, of ophthalmologists, records that traditional vasoconstrictors were avoided because of rebound redness and tachyphylaxis.

The newer type is a highly selective alpha-2 agonist at low dose. A 2022 review reports that trials showed it reduced redness for up to 8 hours with minimal rebound, and the 2026 review notes no tachyphylaxis over 29 days but that longer-term effectiveness has not been evaluated. Whether that suits a particular eye is a question for a consultation, not a shopping basket.

There is a second problem. Redness is the signal that tells you or a doctor something is wrong. If a bottle quiets the signal, a corneal infection or inflammation inside the eye can run on while the white looks clear. If the eye is red enough that you want to whiten it every morning, see a doctor about the cause. The lid and skin side of long-running red, itchy eyes is in my article on itchy, flaky red eyelids.

Do antihistamine eye drops help a red eye?

Yes, when the red eye is itchy and allergic. An antihistamine drop blocks histamine, the chemical that drives the itch and the pink swelling in an allergy, and it does not act on blood vessels the way a whitening drop does. If the eye is red but not itchy, it is unlikely to be the right drop.

The NHS says allergic conjunctivitis makes the eyes red and watery and is not contagious, and that pharmacists can suggest antihistamines. A 2005 review in Drugs concluded that when the complaint is isolated eye itching, topical antihistamine drops are often efficacious and clearly superior to antihistamines taken by mouth. The same review notes that tablets can cause drowsiness and dry mouth.

The limits matter. An antihistamine drop treats allergy, not infection, not dryness and not a scratched cornea. If the eye is red and painful, or a few days of the drop have changed nothing, the diagnosis was probably wrong. Eyelid skin reacting to lash products or cosmetics is a separate, common cause, covered in the page on allergic eyelid reactions.

Why are steroid eye drops a problem when bought without a doctor?

Because a steroid drop is a strong medicine that can quietly raise the pressure inside the eye, make cataract more likely and, in a herpes infection, let the infection spread. Steroid drops have real uses, but they need a diagnosis first and a plan to check the eye while they are used.

Pressure. AAO EyeWiki explains that steroids increase resistance to the outflow of fluid from the eye, and that with topical steroid use the pressure rise most commonly occurs between three and six weeks from the start, normalising typically within two weeks of stopping. A 2006 review in Current Opinion in Ophthalmology adds that people with primary open-angle glaucoma, those who are glaucoma suspects and those with a family history of glaucoma are more likely to have a pressure response. EyeWiki also lists diabetes, very young or older age and connective tissue disease among higher-risk groups. Raised pressure that is not treated can damage the optic nerve, which is glaucoma. The only way to know the pressure is to have it measured, and a person buying a bottle off a shelf has no one measuring it.

Cataract. The NHS lists taking steroid medicines for long periods among the things that make cataracts more likely. The page does not separate drops from tablets, so I would not claim a figure for drops alone.

Herpes infection. A red, sore eye can be herpes simplex keratitis, an infection of the cornea, the clear window at the front of the eye. EyeWiki lists blurred vision, photophobia (light sensitivity), pain, redness and tearing as the typical symptoms, which look much like any other red eye. It states that topical steroids are contraindicated in the presence of active epithelial disease, and that a dendritic ulcer, a branching ulcer on the corneal surface, may evolve into a geographic ulcer, a larger and deeper one, especially in patients on topical steroids. A steroid drop can feel as if it is working, because it calms the redness, while the infection spreads underneath.

The word to hold on to is leftover. A steroid bottle from an old prescription, or one passed on by a friend, is not a spare. It was chosen for a specific eye on a specific day. The same caution applies to steroid cream on the thin skin of the lids.

When is a red eye too serious for any drop?

When it comes with pain, light sensitivity, blurred or changed vision, or when you wear contact lenses. Those need an eye doctor the same day, and no drop from a shelf, whitening, antihistamine or steroid, should be tried first.

The American Academy of Ophthalmology advises contacting an ophthalmologist immediately for moderate to severe eye pain, blurred vision, increased sensitivity to light, intense redness, symptoms that get worse instead of improving, or a health condition that weakens the immune system. The NHS red eye page tells people to go to A&E if a red eye comes with any change in sight, such as wavy lines, flashing or loss of vision, if it hurts to look at light, or after an injury or chemical splash, and to seek an urgent appointment if the eye is very painful and red, or if you have a red eye and wear contact lenses, because you could have an infection. Take the lenses out while you arrange it.

If the red eye is a bright red patch with no pain, it may be a burst vessel instead, which is covered in my guide to subconjunctival haemorrhage. A red eye that is not improving after a week or so deserves an examination, not a stronger bottle.

If there are small children at home, the safe storage of eye drops matters too, and Little Eyes 101 has written about keeping eye drops in the house safe around small children. For the wider map, see the eye socket and thyroid section and my hub article on why eyes look tired.