Why Cannabis Causes Red Eyes (And What To Do About It)

Long associated with stoners, red eyes are a telltale sign that someone has been smoking cannabis. It's definitely something most cannabis users are conscious of, as there are often negative social connotations that come with it. It can be especially risky in countries that legally frown upon the use of marijuana.

If you happen to be one of those self-aware stoners, you might wonder: “How does it happen? How can I fix it? Can I even avoid red eyes altogether?”. We're here to put you at ease with answers to all of these questions.

Why does cannabis cause red eyes?

While there is no single, definitive cause behind the eye redness that occurs from using cannabis, there are a few contributing factors. These include:

• Blood pressure changes
• Exposure to smoke
• Dehydration

Arguably the main cause of red eyes from cannabis is the drop in blood pressure that occurs (Richter et al., 2018). As you may know, blood pressure and heart rate initially rise when smoking. However, once the THC has made its way into your system, it will eventually begin to lower blood pressure. During this phase, blood vessels dilate, including the ones in your eyes, resulting in more blood flow to the eyeball.

Simple exposure to smoke is another reason for red eyes. This is especially true when smoking cannabis in unventilated areas; after a while, your eyes will begin to get agitated. Of course, this kind of irritation is not only caused by cannabis smoke. Your eyes may get sore from tobacco smoke or a campfire in the same way.

Couple these factors with simple dehydration, and you've got a red-eye cocktail. Indeed, dehydration plays a significant role in the severity of bloodshot eyes. Not drinking enough fluids will cause your eyes to become dry and irritated, making them appear red as a result. While cannabis does not actively dehydrate you, your body uses water to remove THC from your blood as part of normal metabolism. That, of course, will also play some part in dehydrating you.

Can CBD cause red eyes?

While it’s evident that THC-laden strains give rise to red eyes, how does CBD fare? Fortunately for users of the latter cannabinoid, CBD does not cause red, bloodshot eyes. This is because the way THC interacts with the body is much different from CBD, resulting in notably different outcomes.

Is it only smoking cannabis that causes red eyes?

Do different cannabis consumption methods affect whether your eyes get red, or how red they get? Although there don't appear to be significant differences, there are some nuances that you should know.

💨 Vaping

Similar to smoking, vaping is a surefire way to get red eyes. Of course, there's no actual smoke involved in vaping, so that is a positive in terms of avoiding eye irritation. But the fact that more cannabinoids are preserved during vaping means you get more potent hits from the same amount of cannabis. This, in turn, results in more THC in your bloodstream, which leads to lowered blood pressure, and, ultimately, bloodshot eyes.

🧁 Edibles

Edibles don't produce any smoke (unless you're a terrible baker), so that won't be a contributing factor. You can, however, accidentally consume more cannabis than you normally would if you aren't watching your intake. So although it may feel counterintuitive, potent edibles can actually be one of the biggest culprits of super-red eyes.

🩹 Transdermal patches

Surely putting cannabis on your skin is a safe way to go? Well, unfortunately, even transdermal patches containing THC may still give you red eyes. Once the THC has been absorbed into your body, it will cause the same reaction as smoking or vaping. Your blood pressure will eventually drop, causing your capillaries and blood vessels to dilate.

Tips for getting rid of red eyes from cannabis

So, what can you do to alleviate post-toke eye redness? Here are a few suggestions to treat those bloodshot marbles.

✅ Hydrate

As we've highlighted, dehydration can play a role in the severity of bloodshot eyes. Being dehydrated can make your eyes dry and irritated even before you've had the chance to smoke, vape, or eat your delicious edibles. As classic stoner wisdom dictates, staying hydrated is essential. This will not only help your eyes, but also has the potential to curb other side effects of cannabis, such as cotton mouth.

✅ Use eye drops

If you find your eyes are bloodshot and you're in need of a “quick fix”, eye drops could make all the difference. Whether you've got to meet your partner's parents or have a surprise meeting with your boss, use drops to keep your eyes lubricated. They'll also act as a natural defence against smoke. Personally, we recommend Open Your Eyes—a product engineered specifically for those prone to getting red eyes.

Open Your Eyes

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✅ Wear sunglasses

Okay, while this isn't strictly a way of treating red eyes, you can always opt to disguise those bloodshot eyes by donning a cool pair of sunglasses. It may sound a little silly, but it works in a pinch if you need to go out and you're self-conscious about looking high. The fact that you're toasted can remain your little secret!

✅ Give your eyes time to recover

Last, but by no means least, simply give your eyes time to recover. Whether this is stepping outside to catch some fresh air during a smoking session (especially if in a poorly ventilated room) or taking a quick nap, it may make all the difference. Of course, pacing yourself and being mindful of your intake will make a huge difference too.

How to prevent red eyes from cannabis

While there's no way to prevent red eyes completely—aside from removing THC from the equation entirely—there are some steps you can take to minimise the severity.

Consider low-THC strains

Opting for strains with lower levels of THC, or simply consuming less of your THC-laden herb, could be the key to partial red-eye prevention. Now, you might have a proclivity for stronger strains, but if you're finding red eyes to be a real issue, go for a milder option to see how that suits you. Luckily for you, we're familiar with some high-quality low-THC options you could give a shot!

Shield your eyes while you smoke

By this point, it's pretty safe to say that THC is the main culprit when it comes to eye redness from weed. However, that's not to say that smoke doesn't exacerbate matters. As such, another way to partially prevent red eyes is to shield your eyes while you smoke. This doesn't mean you need to wear goggles each time you take a hit, but perhaps make a point to avoid sitting in a cloud of smoke.

Are red eyes bad for you?

The simple answer is no; it's just a natural side effect of enjoying cannabis. From a physical perspective, there is no need for alarm, and the effects are relatively short-lived. It's really only from a social standpoint that some feel bloodshot eyes aren't acceptable. Just ensure you're staying hydrated, and don't hang around in smoky rooms. But also, be sure to keep some eye drops close by for quick relief if you need to look sober.

Regardless of whether you're smoking, vaping, or enjoying edibles, the fact remains that we're all susceptible to bloodshot eyes. Just follow our tips for prevention and treatment, and you'll be well on your way to red eye mitigation. For starters, if you're looking to sample some lower-THC strains, we've got you covered. Head to the Zamnesia Seedshop and get paired with a cultivar that's got a good chance of keeping those bloodshot eyes at bay.

Adam Parsons

Professional cannabis journalist, copywriter, and author Adam Parsons is a long-time staff member of Zamnesia. Tasked with covering a wide range of topics from CBD to psychedelics and everything in between, Adam creates blog posts, guides, and explores an ever-growing range of products.

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