Does CBD Make Your Eyes Red? Debunking The Myth

Most weed smokers are familiar with the red eyes which are a telltale sign of marijuana use. They’re a particular problem for stoners who want to hide their cannabis use from employers, family, or friends.

There’s no reason to hide CBD use from anyone, of course, since the cannabinoid is non-intoxicating and legal in almost every Western nation. Even so, it’s understandable that some who are thinking about trying a CBD product wonder about potential side effects — including whether their eyes might become red or dry.

The news is good: they won’t.

The “red eyes” associated with cannabis use can be blamed on the THC that gives marijuana its psychoactive properties. THC often increases blood pressure and heart rate, causing blood vessels to dilate and increasing blood flow in the eyes. That makes eyes look bloodshot.

CBD is very similar to THC, but it has different effects because it interacts with different receptors in the body. It doesn’t immediately boost blood pressure the way that THC does, so vessels in the eyes don’t expand with blood to make the eyes appear red. If you’ve heard that CBD can make your eyes red, it’s just a myth based on a misunderstanding.

CBD and THC do share one eye-related side effect — they can both make your eyes dry. It’s not fully understood why that happens, but the substances do interact with the body’s system that regulates “tear film,” tears that are produced to protect the eyes. CBD can make your throat dry too, for similar reasons.

If you’ve used CBD and your eyes appear red, it’s almost certainly due to a different issue. Allergies, eye strain, contact lenses, a foreign body in the eye, or dry eye syndrome are among the common causes, but if you’re experiencing serious or long-lasting pain along with bloodshot eyes, it’s best to see a doctor or another healthcare professional.

Curious about CBD, THC, cannabis, or red eyes? We’ve got all the details below.

CBD vs. THC

Cannabis and hemp plants belong to the same plant family, Cannabis sativa. They’re similar in almost every way, but there’s one important difference: their cannabinoid content.

Both hemp and cannabis contain more than 100 different plant compounds known as cannabinoids. The two major cannabinoids are THC (tetrahydrocannabinol) and CBD (cannabidiol), and they each appear to provide a large number of medical benefits. However, THC makes users high because of the way it interacts with the body. CBD is non-intoxicating.

Cannabis plants are loaded with THC and have very little CBD content. It’s the opposite story for hemp plants, which are high in CBD (no pun intended) and have extremely low THC levels. That’s why marijuana harvested from cannabis plants delivers psychoactive effects. Cannabidiol is extracted from hemp, so it doesn’t contain enough THC to impair users.

Both of the cannabinoids we’re discussing provide their apparent benefits in similar ways, interacting with one of the body’s most important systems. There’s a key difference there as well, though.

The endocannabinoid system (ECS) regulates the majority of the body’s major functions, governing everything from thinking and memory to sleep, pain, and immunity. The ECS is composed of two elements: the neurotransmitters that carry control messages, and the receptors that send and receive those messages.

The neurotransmitters are molecules produced in the body known as endocannabinoids. As you might guess from their name, their chemical structures are almost identical to those of cannabinoids like THC and CBD. And that allows the cannabinoids to interact with ECS receptors once they’re inside the body.

That’s where the THC/CBD difference we mentioned really matters. THC binds to one set of receptors (the CB1 receptors) located in the brain and nervous system; CBD mostly interacts with a different set of receptors (the CB2 receptors) in the rest of the body.

CB1 receptors primarily control cerebral functions, which is why THC can alter cannabis users’ thinking, memories, and perceptions. CB2 receptors are in charge of functions like inflammation and immunity, explaining why CBD doesn’t intoxicate users even though it’s believed to have major medical benefits.

With that background information out of the way, let’s talk about bloodshot eyes.

What Causes Red Eyes?

Almost everyone’s had bloodshot eyes at one time or another, perhaps from staying out late or drinking too much, or from other common causes.

Many of the reasons that people’s eyes appear red involve everyday occurrences:

• Eye strain
• Broken blood vessels from rubbing the eyes too hard or overexertion
• Contact lenses that don’t fit well or have been worn for too long
• Dry eyes
• Allergies
• Environmental irritants

The treatments for those issues are generally simple: resting the eyes (or simply resting), leaving the contacts out for a while, using eye drops, taking allergy medications, or leaving the offending environment. The red eyes should disappear shortly.

Other causes of red eyes may require medical intervention. They include:

• Foreign object in the eye
• Conjunctivitis
• Blepharitis (inflammation of the eyelids)
• Uveitis (inflammation between the retina and the white of the eye)
• Scleritis (inflamed white of the eye)
• Glaucoma

Most of those conditions (except for an object in the eye) are caused by medical problems or diseases, many of them serious. If eye redness is accompanied by serious pain, or doesn’t quickly ease with eyedrops or other home remedies, it’s best to see a doctor or specialist quickly.

We didn’t include THC or CBD use on those lists. We’ll address them next.

THC, CBD, and Red Eyes

As mentioned in the introduction to this article, cannabis use can lead to bloodshot eyes, but CBD products don’t cause the same effect. Here’s why.

THC Use and Red Eyes

Marijuana users know when they’re high. Poor coordination, confused or racing thoughts, and slow reaction times are some of the first signs of weed that’s kicked in. It’s not quite as easy for other people to tell if those users are high, particularly if they’re experienced smokers.

Several outward signs can be clues. Some users may not be able to hide the weed aroma, others may slur their speech or sweat profusely. The most obvious indications that someone’s been partaking, though, are diluted pupils or red eyes. They’re extremely common side effects.

What explains the bloodshot eyes associated with cannabis use?

THC, as we’ve explained, interacts with the endocannabinoid system’s CB1 receptors. Among their many other duties, those receptors control blood pressure and heart rate. When THC binds to the receptors, both blood pressure and heart rate are likely to increase in the short term.

That leads to a daisy chain of effects in the body. Blood vessels dilate (become wider) and blood flow increases; when the faster-moving blood reaches the eyes it increases interocular pressure, causing blood vessels in the eyes to expand. And when there’s more blood flowing through the eyes, they look redder than usual.

It’s only a short-term effect, and there’s some evidence that cannabis use may help lower blood pressure over the longer term. That knowledge, though, doesn’t help weed users trying to act normal after secretly smoking up.

CBD Use and Red Eyes

CBD products don’t cause bloodshot eyes, and the explanation is a short one.

Cannabidiol interacts primarily with the ECS’s CB2 receptors, which don’t regulate heart rate or blood pressure. So when you use CBD oil, capsules, edibles, vapes, or other products, you won’t notice your body feeling any different and nothing will trigger the blood vessel dilation that can cause red eyes.

Some research shows that cannabidiol may provide long-term benefits for blood pressure levels and cardiovascular health. But those are long-term effects; in the minutes or hours after using CBD, nothing will happen that could make users’ eyes red.

Side Effects of CBD Use

The World Health Organization (WHO) has made it clear that there is “no evidence of public health-related problems associated with the use of pure CBD.” And no serious side effects have been documented in those who’ve responsibly used cannabidiol.

We know that CBD doesn’t cause bloodshot eyes — but that doesn’t mean there are no side effects whatsoever. For starters, some users may notice the same dry eyes that cannabis users often experience. The two cannabinoids’ interactions with the ECS appear to affect the body’s ability, or lack of ability, to produce tears.

CBD products may also cause dry mouth, fatigue, diarhhoea, or other gastrointestinal issues. However, those side effects are minor, and most users will never experience them. They’re only likely to hit people who are new to CBD, those who take extremely high doses of cannabidiol, and those who take high doses every day.

CBD could be a bad choice for a small group of patients dealing with medical issues like liver or kidney disease, and it does have potentially problematic interactions with some common medications. Anyone considering CBD use would be smart to consult their doctor before starting.

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