context: If you have dry, irritated eyes, you might head over to the drugstore to pick up some eye drops. Just a quick trip, you think, until you find yourself standing before endless shelves of options. With all the different types out there, does it matter which you choose? Yes, it definitely does. You use different types of drops to treat different problems, like allergies vs. dry eyes. And the wrong ones may make your symptoms worse. For the most part, there are three main types of eye drops: Artificial tears Allergy drops Anti-redness drops Some eye drops might do a combination of things, but if you understand these basic types, you'll know how to choose wisely. You might also notice some natural, homeopathic, or herbal eye drops. Generally, there's just not a lot of evidence about how well these really work. When to use them. Artificial tears are your go-to drops for dry eyes. Their main job is to keep the surface of your eyes nice and moist. What's in them. They try to mimic real tears, but it turns out, that's pretty complicated. So various brands use different mixes of ingredients, such as: Lubricants to keep your eyes moist (all artificial tears will have some) Electrolytes, like sodium and potassium, which can help heal the surface of your eye Guar gum, found in more oily drops. It can be a big help if you get dry eyes because your tears dry up quickly. Preservatives to keep bacteria from growing in the bottle of drops You may need to try different brands to see which one works best for your eyes. Watch out for preservatives. Artificial tears with them can be great because they're often cheaper. But for some people, they can make dry eyes worse. Some people are allergic to preservatives, and others may find that they irritate their eyes. Avoid artificial tears that contain preservatives if: They bother your eyes. Your dry eye is severe. You use drops more than four to six times a day. When you're looking for preservative-free eye drops, note that they don't come in the typical eye drop bottle. You usually find them in single-use vials instead. You snap the lid off, put the drops in, and throw out the vial. They also tend to be more expensive than other kinds. When to use them. These are the drops to reach for when you need relief from itchy, watery, red eyes caused by pet dander, pollen, molds, and other common allergens. What's in them. When your body has an allergic reaction, it releases a bunch of histamines. That's what triggers the runny nose, itchy eyes, and all the rest. The key ingredient in allergy eye drops is a drug called an antihistamine, which blocks histamines from doing their work and prevents allergy symptoms. Some newer allergy eye drops, called mast-cell stabilizers, work by stopping your body from making histamines in the first place. When to use them. Also called decongestant drops, they can help clear the redness out of your eyes. But use with caution. If you put them in for more than a few days, they can irritate your eyes and make the redness even worse. Another problem: If you use them often, your eyes get dependent on them and may get red when you stop using them. Avoid these drops if you have dry eyes. Sometimes, anti-redness drops also have antihistamines in them, which can relieve itchiness from allergies. But again, you're limited in how much you can use them without bothering your eyes. You're typically better off with allergy drops. What's in them. These drops use an ingredient called a vasoconstrictor. It shrinks the blood vessels on the surface of your eye. That makes the redness go away. If you wear contact lenses, it can make choosing eye drops a little harder because not all go well with contacts. When your contacts are dry, try rewetting drops made for your type of contacts. Check with your doctor before you use any other kinds of drops, and avoid those with preservatives. Sometimes, dry, red, or irritated eyes come and go and they're not much of a problem. In other cases, you may have a medical problem that needs more than just drops. See your doctor if you have eye problems that don't go away, even after taking drops for a while. Also, see her if taking drops makes your eye problem worse or affects your vision.