Why does weed make your eyes red?
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- Under pressure: lower blood pressure and dilated capillaries
- Do edibles make your eyes red?
- The redder the better?
Among the most common effects of marijuana use (and telltale signs you’ve recently partaken) is red, bloodshot eyes. It’s to be expected, sure, but that doesn’t answer the mysterious question pondered by generations of stoners: why does weed make your eyes red?
For weed novices, the onset of bloodshot eyes could cause a panic-induced internet search asking “ can smoking weed damage your eyes? ” Thankfully, as those who regularly consume cannabis can tell new users, there are no serious health risks associated with your sudden red-eyed circumstance. You’re probably not experiencing an allergic reaction or some bigger complication. Some might poke fun or chastise you for sporting your so-called “ weed eyes ” in public, but otherwise, it’s a completely natural occurrence that transpires after smoking cannabis.
In fact, your eyes turning red has nothing to do with the act of smoking at all.
Under pressure: lower blood pressure and dilated capillaries
After consuming a cannabis-based product (flower, concentrate, edible, etc.), users generally experience an increase in heart rate and blood pressure. This effect is due to the plant’s cannabinoids, which are chemical compounds responsible for some of the therapeutic and medicinal benefits of cannabis, and their initial interaction with the body. This rise in blood pressure and heart rate is comparable to normal physical activities like exercise or sex.
It generally takes about five to ten minutes for users’ heart rates to return to normal and for blood pressure to begin to decrease. As the blood pressure lowers, the blood vessels and capillaries dilate, including the ocular capillaries . The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red and also reduces intraocular pressure.
The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red in the process, and also reduces intraocular pressure. Photo by: Gina Coleman/Weedmaps
In fact, according to Dr. Melanie Bone, a board-certified OB-GYN who practices in West Palm Beach, Florida, “It’s cannabis’ ability to reduce intraocular pressure in the eyes that makes it a potentially viable treatment for glaucoma , a group of eye disorders that causes damage to the optic nerves which can eventually lead to blindness. It also happens to explain why your eyes become bloodshot after smoking cannabis.”
Evidence that the THC found in cannabis can lower intraocular pressure (IOP) is a major reason why many glaucoma patients have attempted to use medical marijuana to treat and relieve symptoms of the disease. It’s important to know that some studies have contradicted or added a caveat to the claim that cannabis is beneficial for glaucoma. For instance, a 2018 study conducted at Indiana University found that cannabidiol (CBD), the non-intoxicating cannabinoid found in marijuana, could potentially worsen the condition by increasing eye pressure . More research into the use of cannabis for glaucoma treatment is needed.
Do edibles make your eyes red?
Similar to smoking cannabis, ingesting edibles could also make your eyes turn red. Again, this depends on the amount of THC consumed. Remember, it’s not the smoke itself that makes your eyes red, but rather the ability that cannabinoids have to lower blood pressure, causing blood vessels and capillaries to dilate.
The redder the better?
The amount your blood pressure is lowered and how red your eyes become depends on the amount of THC you consume.
Tetrahydrocannabinol (THC), the most common cannabinoid in the plant, is responsible for the intoxication associated with smoking cannabis. The greater the concentration of THC in a cannabis product, the stronger the effects and the redder your eyes become.
The greater the concentration of THC in a cannabis product, the stronger the effects and the redder your eyes become.
So, red eyes can act as a sign that your cannabis has a high cannabinoid content (i.e., it’s potent). In other words, if your eyes are noticeably bloodshot after consumption, there’s a good chance you’ve landed yourself some highly potent weed.
Other than being a dead giveaway that you’ve recently consumed cannabis, you have no reason to be concerned about the redness of your eyes. Cannabis-induced eye redness will typically only last a few hours and can easily resolve if you have the right tools at your disposal.
It isn’t a bad idea to have eye drops (or some sunglasses) on hand. Look for eye drop brands that are specifically designed to reduce eye redness. There are other methods that could potentially help combat cannabis-induced bloodshot eyes, including staying hydrated, washing your face and eyelids with cold water, or simply consuming cannabis products with lower THC levels.
Ever wonder why using marijuana or cannabis makes your eyes red or bloodshot? Discover why weed gives you bloodshot eyes.
Why Do Eyes Turn Red After Smoking Weed?
Friday February 3, 2017
T he most well-known identifier of being high is the classic red eye look. Some users can experience a “worse” reaction than others, but it’s one of the physical markers that you just can’t avoid.
Why do you get red eyes after smoking weed ? Some say it’s because of the smoke in the air—that the lingering particles are to blame for irritating your eyes. Others say that red eyes are considered to be an allergic reaction to smoking. And while both are logical and possible, there’s a more scientific reason behind it.
Red eyes are caused by a change in pressure. The main psychoactive endocannabinoid in marijuana, THC, gets into your system and causes your blood pressure to decrease. As a result, your inner-eye pressure lowers and causes blood vessels and capillaries to dilate. This allows blood flow to increase and gives small blood vessels more room to expand, resulting in what we see when we look in the mirror.
But the same scientific reasoning above is why cannabis can help glaucoma patients: A condition that causes increased pressure in your eye and on your retinal nerve. It can often lead to blindness, but researchers since the 1970s have found a positive link between marijuana and glaucoma since the drug can help lower intraocular pressure. This only lasts a few hours so it certainly isn’t a treatment, but it’s a good option for patients in pain.
Even retinal damage, one of the most common eye problems, can be improved with the use of marijuana. Studies show that cannabis has neuroprotective and antioxidant properties that encourage retinal health and prevent vision loss.
Your red eyes aren’t anything to be ashamed of; many people experience red eyes — plus it’s just marijuana doing its medicinal thing. But it can be a burden if you’re about to walk into work or have dinner with the grandparents. Remember that it’s due to the endocannabinoids within cannabis, so it can happen with any form of consumption.
The good news is that you can do something about it. And although you may already have your own ways to remedy red eye-syndrome and being high in general, here are a few of the most common methods to avoid getting red eyes after smoking weed:
- Eye drops. P roducts (like Visine) are the oldest trick in the book and work within minutes since it helps to constrict blood vessels. (Remember that over-using these products can be detrimental.)
- Drink water. Unrelated to cannabis, redness in the eyes is sometimes associated with dehydration. Avoid caffeine and s tay hydrated to eliminate the redness .
- Consider low THC strains. If you’re really looking to limit the amount of redness, consider a strain without high levels of CBD, CBN or THC.
- Cold compress. Cold water will soothe irritated eyes and can help decrease swelling and the amount of blood flow.
- Sunglasses. You may look ridiculous, but if nothing else works you can easily use your shades. The sun may be an irritant in and of itself, so avoid harmful rays whenever possible.
- Wait. Generally, your eyes will only stay red for a few hours so just stay where you are and wait it out.
You may have heard that consistent users have developed some form of “resistance” to experiencing red eyes. (I guess there’s only one way to find out for yourself.) But at the end of the day, it’s all harmless and red eyes are just a side-effect, so there’s no need to worry if you don’t have clear eyes all of the time. Plus, it’s good to know that everyone will be affected differently based on tolerance, strain types, genetics and overall health so don’t count red eyes as a bad thing .
A born and raised Hoosier and Indiana University alumna, Morgan Smith is a freelance writer and editor based in the Denver area. Morgan has worked with B2B, nonprofit and regional publications, but especially enjoys learning and educating others about the inner-workings of the cannabis industry. Her freelance writing supported her recent six-month solo backpacking trip to South America where she climbed volcanoes, played with llamas and jumped off a bridge.
Probably the most well-known identifier of a marijuana high is the classic red-eye look. But what is the science behind why red eyes occur? Here's a breakdown, plus a few common remedies to help avoid red eyes after smoking.