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Why Smoking Cannabis Causes Red, Bloodshot Eyes

October 13, 2016
Why does smoking weed make your eyes red?
Red eyes are typically a classic, telltale giveaway that someone’s smoked cannabis. For certain individuals, it’s a guaranteed occurrence, while for others who seem to be less sensitive, red eyes may come and go depending on the quantity or quality of the cannabis they consume.

What causes this common reaction? A few factors may come into play.

The primary cause for reddening of the eyes after smoking cannabis also happens to be the main reason that the plant is famous as a treatment for glaucoma. In short, THC lowers blood pressure, which in turn causes blood vessels and capillaries to dilate. The ocular capillaries dilate, which increases the flow of blood to the eyes and reduces intraocular pressure. Increased blood flow creates the redness, while the decrease in pressure is the same effect that benefits glaucoma patients.


Can CBD and THC in Cannabis Be Used for Glaucoma Treatment?

This reaction explains the variations in the intensity of red eyes. An individual may smoke a low THC strain one day and experience little to no red eyes, while the next day their eyes may be beet red after ingesting a high THC strain.

Additionally, this explanation accounts for why red eyes can still occur even with the lack of smoke, such as when eating edibles. It’s not the smoke that makes your eyes red, but the cannabinoids.

That being said, it’s possible for some to have an allergy or irritation to cannabis or to smoke in general, and have increased redness of eyes for this reason. However, for these sensitive individuals, the experience would likely be a universal reaction to smoke, be it cannabis, tobacco, or perhaps even incense.

How to Get Rid of Red Eyes from Cannabis

Eye drops for red eyes from smoking weed
The cause for red eyes from cannabis is a harmless, even perhaps beneficial one, but that doesn’t necessarily make it a welcome reaction to all. There are a few simple steps one can take to minimize or reduce redness of eyes during or after smoking.

  1. Opt for low or no THC strains. Strains high in CBD, CBN,  and the like may be a desirable alternative for those looking to lessen red eyes when toking.
  2. Have eye drops on hand, especially brands specially formulated to reduce eye redness.
  3. Stay hydrated by drinking plenty of water. Increasing your fluid intake may help alleviate the dryness you experience.
  4. Simply let it run its course and plan smoke sessions for leisurely moments spent at home. Ultimately, red eyes are not harmful and come with no negative outcomes (other than the dated stigma associated with them).

The next time a glance in the mirror reveals a pair of bright red eyes after a smoke sesh, just remember that a little extra blood flow is nothing to worry about!

Rae Lland's Bio Image

Rae Lland

Rae Lland is a freelance writer, journalist, and former editor for Weedist and The Leaf Online. With a focus on culture, music, health, and wellness, in addition to her work for Leafly, she has also been featured in numerous online cannabis publications as well as print editions of Cannabis Now Magazine. Follow her on Instagram @rae.lland

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  • This is a very informative post.
    The Best 5 Home Remedies for Eye Infection..

    Your eyes can get infected due to allergies, certain types of viruses, bacteria or due to other microbiological reasons. Common eye infections are conjunctivitis, sty, keratitis or orbital cellulitis.

    Until you get to a doctor, here are a few inexpensive and natural home remedies which will help reduce the symptoms:

    #1 Warm compress for eye

    A warm compress is very useful if you have a sty or are suffering from conjunctivitis.

    The heat in a warm compress increases the blood circulation and helps in healing. It also prevents further infection and reduces pain and swelling.

    Common eye infections are conjunctivitis, preseptal cellulitis, keratitis or iritis. Here are a few natural home remedies for eye infection.


    a) Take a clean towel and dip in hot water for some time, then wring it thoroughly to squeeze out excess liquid.
    b) Fold the moist and warm towel in a square and hold it against your closed eyelids for 5 minutes.
    c) Repeat 4-5 times
    d) Clean any oily residue from your eyelids and eyelashes with a different clean cloth.
    e) Repeat many times during the day to get relief.

    Follow this link for the rest of home remedies:

  • abie cee

    “THC lowers pressure, which in turn causes blood vessels and capillaries to dilate”… If that were true, every relaxed individual would also have those supposed “red eyes” so often attributed to cannabis, because relaxation also causes blood vessels and capillaries to dilate.

  • abie cee

    Cannabis does not cause red eyes. This article is BS. So is the person who deleted my comments.

  • Jay Buddington

    Do you think it is possible that the mere fact of smoke getting into one’s eyes causes the bloodshot eyes..?? Does the consuming of cannabis edibles or oils cause the same bloodshot eyes..?? I would say, YES to the first question posed, and NOT to the latter question..!! Tobacco cigarette smoking is usually not the same passionately involved technic as smoking cannabis, not doubled over and cupping the burning herb, and not double inhaling through the nose, that complimentary second intake hit up the nose just after the end of the lip toke, french inhaling and like methods, snorting roaches, hot boxing, and trying to capture every last molecule every which way you can… Anyone remember Shotguns..??

    • Fwee Wub

      I am a regular cannabis user and very rarely get red eyes from smoking or vaping, but when I consume edibles I invariably get very, very red eyes.

      • John Noan

        You and me both, Jack.

  • Chas_M

    Not accurate information. I get red eyes from CBD oil, with no discernible THC at all.