High Eyes: Why They’re Red & How To Prevent It

Last Updated on Oct 6, 2022 by Mark Conklin, RN, MHA

Marijuana has been around for centuries, and people have long debated its effects on the body. Today, we know that marijuana does have a physical impact on the body- primarily in the eyes (high eyes).

When someone smokes marijuana, their eyes become red and irritated. In this article, we will explore why marijuana makes your eyes red and how to treat it if it happens, as well as how to prevent it before it does.

Topics we’ll cover include:

Why Does Marijuana Make Your Eyes Red?

High Eyes on woman

The tell-tale red eyes of someone who’s high on marijuana are often blamed on smoke irritation. But, that’s a common misconception. Marijuana makes your eyes red for the same reason it’s used to treat glaucoma— a physiological mechanism known as vasodilation.

Vasodilation is the dilation, or widening, of blood vessels. When blood vessels widen, they allow more blood to flow through them. This increase in blood flow can cause redness and swelling in the eyes.

The red eyes is triggered by the main psychoactive ingredient tetrahydrocannabinol (THC). THC is just one of 113+ active compounds in marijuana, known as cannabinoids. These cannabinoids interact with cannabinoid receptors throughout your body, particularly your eyes.

When THC binds to cannabinoid receptors, it lowers our blood pressure, which in turn causes the dilation or expansion of blood vessels and capillaries. In the case of your eyes, the ocular capillaries dilate, causing an influx of blood flow to the area, creating a red appearance of the sclera (aka the white of the eyes). That’s why we call it “bloodshot” eyes.

For glaucoma patients, the THC-induced vasodilation of ocular capillaries also temporarily reduces intraocular pressure. High intraocular pressure is the main symptom of glaucoma and can contribute to optic nerve damage and vision loss. Therefore, reducing this pressure is a key priority of glaucoma treatment. One study, published in the Journal of the American Medical Association, reported that smoking marijuana reduced intraocular eye pressure by up to 30%.

Do Edibles Make Your Eyes Red?

This is a common question, usually because many people assume it may be the smoke that causes eye redness. But edibles, just like topicals and tinctures, can also contain THC, so they  can also cause red eyes through vasodilation.

Why Are My Eyes So Red One Day, But Not the Next?

While red eyes are a dead giveaway that someone has been smoking marijuana, it’s not always a guaranteed symptom. That’s because each strain of marijuana has a different concentration of THC. Hence, someone may experience intensely red eyes after ingesting a high THC strain, but barely notice the difference after a low THC strain.

However, there’s more at play than just THC content. As you may have experienced yourself, the same cannabis strain can have different effects on different people. These varying effects are due to a number of individual factors, including gender, genetics, and overall health.

THC And Blood Pressure

Whether a person experiences red eyes or not is primarily influenced by their blood pressure. For instance, people with high blood pressure need more THC to lower their blood pressure enough to cause intense bloodshot eyes. Although, those with naturally low blood pressure can quite easily experience terminator red eyes.

With that being said, people with allergies to marijuana or smoke, in general, can experience exacerbated symptoms. But for users with an allergy, typically, red eyes are the least of their concerns.

Treatment: How to Get Rid of “High Eyes”

Red “high eyes” are a completely harmless side effect of marijuana and usually aren’t a problem. But, they can be a nuisance, especially for those who need to medicate with cannabis to get throughout the day.

Due to the persistent stigma surrounding marijuana, attending work or university with bloodshot eyes can trigger unwanted attention and potential legal questioning. Fortunately, there are some strategies to reduce the severity of redeyes after using marijuana.

Treat With Eye Drops To Stop Red Eyes When High

Over-the-counter eye drops designed to treat allergies, redness, and itching are the most effective way to alleviate red eyes. Basically, all variations of eye drops contain tetryzoline, which is an alpha-agonist that constricts blood vessels. Essentially, this reverses the dilation caused by THC, which then reduces blood flow to the eyes and the accompanying redness.

Home Remedies

Other items you might have lying around the house can also trigger vasoconstriction. For instance, stimulants such as caffeine can help induce vasoconstriction. Therefore, drinking a fresh cup of coffee or enjoying a few squares of dark chocolate might help alleviate red eyes.

Coldwater is also a strong vasoconstrictor. It forces the body to send blood toward our core to protect vital organs as part of a survival instinct. Splashing cold water on your face or placing an ice pack across your eyes can achieve this effect. If you’re brave enough, a cold shower or ice bath will also do the trick.

Wait for Symptoms to Subside

The redness will eventually subside and return to normal. Therefore, you can be patient and simply wait for THC to run through your system. The key question is, however, how long do your eyes stay red after smoking marijuana?

Unfortunately, the answer isn’t clear-cut. You may have to wait from 2 to 12 hours, depending on a variety of factors, including the administration route and the dose of THC. For instance, when marijuana is smoked or vaporized, THC is rapidly absorbed into the bloodstream. Effects are felt within 2-5 minutes, peak within 15 to 30 minutes, and usually subside within one to three hours, depending on the dose.

Edible THC, on the other hand, is much slower and longer lasting. It takes effect within 30 to 90 minutes, reaches maximum effect after two to three hours, and can last for four to 12 hours, depending on the dose.

Individual factors, including your tolerance, body weight, and metabolism, also impact the pharmacokinetics of marijuana and will determine how long it will take for your eyes to return to normal.

How Do You Prevent Red Eyes When High?

We’ve covered several ways to treat red eyes, but can this side effect be prevented from occurring in the first place?

Choose Low Thc Strains or CBD

Since THC is the main cannabinoid responsible for red eyes, opting for a low THC strain or using CBD only will minimize the unwanted side effect. Of course, you won’t experience the same psychoactive effects, although high-CBD strains are ideal for days you don’t want red eyes.

Plan Ahead of Time

You may have read that staying hydrated can minimize the redness, but this is entirely false. The next best form of prevention is planning and time management. If you need to use marijuana before work or an important meeting, plan to do so well in advance to allow your body and eyes time to recover.


  1. Does CBD make your eyes red?

    CBD by itself will not make your eyes red. However, if you use a full-spectrum CBD product that contains THC, it’s possible that your eyes may become bloodshot.

  2. Can dehydration cause red eyes?

    No, dehydration cannot cause your eyes to become red. In fact, staying hydrated may help prevent red eyes caused by smoking marijuana.

  3. What’s the best way to get rid of red eyes?

    The most effective way to get rid of red eyes is to use over-the-counter eye drops. These are designed to constrict blood vessels and reduce blood flow to the eyes. Other home remedies, such as cold water or ice packs, may also help. However, the best way to prevent red eyes is to choose low-THC strains or use CBD only.

  4. How long do your eyes stay red after smoking marijuana?

    The answer isn’t clear-cut. You may have to wait from 2 to 12 hours, depending on a variety of factors, including the administration route and the dose of THC. Individual factors, such as your tolerance, body weight, and metabolism, also play a role.

  5. What is the best way to prevent red eyes when smoking marijuana?

    The best way to prevent red eyes when smoking marijuana is to choose low-THC strains.

  6. Can you hide high eyes?

    Yes, there are a few ways to hide high eyes. Wearing sunglasses or using over-the-counter eye drops can help mask the redness. However, the best way to prevent red eyes is to choose low-THC strains or use CBD only.

Howard Seth Meiselman, DO

Medically reviewed by Howard Seth Meiselman, DO — Written by Mark Conklin 

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Mark Conklin, RN, MHA

Mark Conklin is the founder and CEO of Tierra Healthcare Concepts and is also part of the medical team. He has over 25 years of experience in the healthcare field working at the executive management level and as a medical professional. Education RN, BS Biology, and Master of Health Administration course curriculum.

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