Medically Reviewed by
Jason Crawford

Article Last Updated on January 12, 2023

Ending up with red, bloodshot eyes after you’ve just finished smoking a joint is the most obvious tell-tale sign you’ve been hanging out with Mary Jane. Inexperienced users will often think something’s wrong or that they’re having an allergic reaction, when in reality, it’s just a harmless side effect of cannabis.

A lot of long-time weed connoisseurs have learned to embrace red eyes as part of the experience, without giving much thought about it. But, sometimes you have things to do and need to move on with your day without being too obvious. If you’ve wondered how long your eyes will stay looking like two precious ruby stones and what factors influence the duration, then keep reading.

Today, we’ll discuss why your eyes get red in the first place, how long they stay red, and what you can do to minimize the glare. ANd if you’re looking for info about pupils and smoking weed, check out our post on if pupils dilate when you smoke weed.

Why Does Smoking Cannabis Cause Red Eyes?

There is a misconception among inexperienced users that smoking weed causes eye redness due to the smoke, but this isn’t true. The real reason why smoking weed makes your eyes turn red is that THC (tetrahydrocannabinol), the psychoactive cannabinoid, causes temporary changes to blood pressure, which affects the ocular capillaries.

Here’s a more detailed explanation: when you inhale marijuana, it goes straight to your lungs and from there into your bloodstream. When the cannabinoids get into your body, they start interacting with the receptors of the endocannabinoid system. THC, in particular, binds to the receptors in the brain which causes a chain of reactions.

First, the heart rate temporarily increases which also raises the blood pressure. This is when you feel that first rush of the first toke. Then, after about 10-15 minutes, the blood pressure starts going down and the blood vessels dilate. This dilation causes an increased blood flow throughout the entire body, thereby making the white of the eyes (the sclera) appear red. In other words, you get bloodshot eyes.

How Long Does the Eye Redness Last?

How long the eye redness will last after smoking weed will vary upon many factors, but it’s always no less than an hour, at least. You may have noticed already that sometimes your red eyes will stay like that for hours, while other times, it would be barely two hours before they start clearing up. You may have also noticed that the intensity of the redness isn’t always the same.

Truth is, the duration of your ruby-red eyes will always vary. The most obvious factor that affects how long you’ll have eye redness is how much you’ve smoked and the percentage of THC in the weed. 

Some weed users say that the redder your eyes are, the better the weed was, and there may be some truth to that. Strains with more balanced levels of THC and CBD will not cause such intense redness and will not last that long.

Other factors that will influence how long your eyes will be red would be your individual sensitivity to marijuana and tolerance to THC, your age, genetics, and overall health condition. Moreover, people who are prone to allergic reactions to marijuana may be more susceptible to getting red eyes. That being said, as we already mentioned, it ultimately depends on the strain and how it affects the smoker.

Bottom line is, there isn’t one sure way to know but to learn your body’s responses and act accordingly.

Will I Always Get Bloodshot Eyes When I Smoke Weed?

Some inexperienced users seem to think that once you start smoking weed regularly, you won’t get bloodshot eyes as often, but this is rarely the case. Sure, the tolerance you will have built up to THC will make you a little more resilient, but it won’t make you immune to its different effects, such as eye redness.

Red Eyes Can Be Good for Glaucoma Patients

One positive outcome from this side effect of cannabis is that it helps relieve the symptoms of glaucoma, a common eye condition that causes damage to the optic nerves, resulting in increasingly impaired vision. 

The ability of weed to dilate the blood vessels in the eyes results in temporarily decreased intraocular pressure which brings great relief to glaucoma sufferers. Some states even list glaucoma as part of their qualifying conditions for issuing a medical marijuana card.

Is There a Way to Effectively Get Rid of Red Eyes?

While you can’t escape red eyes, you can prevent them from being too prominent by choosing to smoke low THC strains. If you’re lucky, you may end up looking like you’ve just stayed a bit too long on the computer instead of having just enjoyed a doobie.

If you like using strains with higher THC percentage, then you will need to find a way to get rid of the eye redness the best way possible.

Any experienced weed user will tell you that over-the-counter eye drops that are able to constrict the dilated ocular capillaries are your best friend at all times and an essential to have in your pocket (together with your phone, card, and keys). 

Eye drops such as Visine (and the most well-known ones) contain the active ingredient called tetryzoline or tetrahydrozoline hydrochloride which is an alpha-agonist and reverses the dilation caused by THC. Take note, though, that overuse leads to the opposite effect, so only use them as needed.

You can also use other substances that have the ability to constrict dilated blood vessels, such as caffeine. If you find yourself in a situation where you don’t have eye drops, a can of Cola or a cup of coffee can also lessen the appearance of red eyes. Add a splash of cold water to that for double action, as cold temperatures can also help with the shrinking of blood vessels.

Finally, you can just wait it out if you have time. Sometimes it’s annoying, but other times you can simply distract yourself with something else and so you won’t even think about it. Plus, as we said, it’s a part of the process, so you might as well embrace it.

Bottom Line – How Long You’ll Stay Red-Eyed Always Changes and Depends on Many Factors

Getting bloodshot eyes when you use weed is no one’s favorite side effect, but it’s there, as a part of the experience. Needless to say, it’s a harmless reaction to your body from the temporary changes that THC imparts to the body. So, the best that you can do is to use some vasoconstricting eye drops or smoke low THC-strain cannabis. 

Whether you’ll get intense red eyes or just slight reddening depends on many factors and will vary from person to person, so it’s better to learn how your own body reacts so you can deal with it more efficiently.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.