Why Does Weed Cause Red Eyes?

Why Does Weed Cause Red Eyes?

Weed can have some amazing effects on our body: relaxation, euphoria, pain relief. Then there are the not so good side effects, like drowsiness, dry mouth and the tell tale sign of a stoner: red eyes. We’ve all been there at one point or another: trying to keep our cannabis use discreet, only to have our heavy lids and glassy bright red eyes give us away without even saying a word. No stoners are safe! Not baby stoners, trying to hide it from their judgey relatives, nor parents who medicate mid day to help with mommy brain. Sooner or later, your ruby red eyes will give you away. But have you ever wondered why, exactly, that is? What about weed makes our eyes glow like red embers? Let’s dig in and get to the bottom of weed induced red eye, and what you can do to fight it. 

Weed Causes Changes In Your Body

The answer to the question of why weed makes our eyes red is a complicated one, mostly because weed is a complex plant. THC and other cannabinoids cause changes in your body that set off chain reactions. When you smoke weed, your blood pressure and heart rate increase, causing blood vessels to constrict. A few minutes after you finish smoking, your blood pressure will begin to drop. Low blood pressure causes capillaries, the thin veins in our eyes, to dilate or open, which allows blood to rush into our eyes, turning our eyes red.


Studies have found that THC works very similar to anandamide, a neurotransmitter sometimes called ‘the bliss molecule’ for its ability to trigger feelings of happiness and mental wellbeing. These chemicals work together to accelerate the drop in blood pressure and heart rate, causing a rush of blood to the eyes and rapid appearance of the bloodshot eyes often associated with weed.

why do i get red eyes when i don't smoke

Many people are under the false impression that it’s actually the smoke from our joints or bongs that turn our eyes red.  Even though smoke is known to be irritating to eyes, it may surprise you to find out that it’s not the smoke that’s making your eyes red, it's actually the THC. That's why, no matter how you choose to ingest your weed, whether you’re inhaling, smoking, eating or drinking THC, your eyes will eventually become bloodshot and give you away, it just depends how long it takes the THC to break down and be absorbed by your body.

Eating edibles takes the longest to hit because it takes much longer for THC to be absorbed by the digestive system than it does the respiratory system. That's why you get red eyes almost immediately after smoking weed but not for an hour or two after you eat an edible.


The time it takes for your eyes to become bloodshot is dependent on a few different factors and not just on your method of consumption. The potency of your weed and the amount you consume are the biggest determining factors when it comes to red eyes. Because red eye is caused by THC, the more you consume, the faster your eyes will turn red. THC isn’t the only cannabinoid that can turn your eyes red though. Other cannabinoids like CBD and CBN are also part of the equation because they also influence the effects you experience from a particular strain. These other cannabinoids will also affect the length of time it takes your eyes to turn red.

Though more research is still needed, scientists know that another huge factor that determines how red THC will make your eyes is your individual blood pressure. A person with very high blood pressure likely won’t experience severe red eye. This is because their baseline blood pressure is too high to be lowered enough to dilate their blood vessels. A person with average blood pressure will experience more red eyes than a person with high blood pressure, while a person with low blood pressure will not only experience red eyes, but may also become dizzy as their blood pressure drops even lower than normal.

Health Benefits

It may sound crazy, but the same process that makes our eyes bloodshot after we smoke or vape or eat edibles actually has real world health benefits. Glaucoma was one of the earliest conditions where the use of cannabis was applied medicinally. Glaucoma is a progressive condition that destroys the eye’s optic nerve as a result of fluid built up in the eye. The fluid buildup increases pressure in the eye and damages the optic nerve. 

The process that causes our eyes to get bloodshot from weed works by lowering blood pressure, allowing blood to move more freely through less constricted capillaries. This is the same process that also relieves the pressure in the eyes of glaucoma patients and is what makes cannabis so effective at treating glaucoma and other ailments in the ocular cavity.

What Can You Do About Red Eyes?

If you ate an edible before a big family event and are freaking out about your red eyes, you can relax. It turns out, it’s actually pretty simple to get your eyes to go back to their normal color, no matter what shade of red they’ve turned. Since eye redness is caused by dilated blood vessels, all you need to do is constrict the blood vessels in your eyes and the redness will dissipate. There are a wide variety of over the counter eye drops for allergies, itchiness and redness that will do a great job of making your eyes look normal again. Just don’t be fooled into thinking that just because your eyes aren’t red anymore that you’re no longer high, cause that's definitely not the case. Any over the counter eye drops with the ingredient tetryzoline will work effectively, and in a pinch, you can also use ice to constrict the blood vessels and relieve your red eye.

Reading next

Weedsy Has Everything You Need to Light Up for Independence Weekend
What Does Cannabis Rescheduling Mean For You

Leave a comment

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Premium Cannabis Flower.

Made With Love.

Made For Everyone.

Multi-State Operator.