why do eyes turn red when smoking weed

Why Cannabis Causes Red Eyes

Red eyes are the most obvious giveaway that someone has just polished off a fat joint. Although no big deal when you’re in the right setting, red eyes can give you away when you’re trying to be low-key about your passion for weed. Use the tips mentioned below to reduce eye redness after a joint, and learn how to prevent it in the first place.


After consuming cannabis, herb-lovers exhibit several signs that make it obvious they’ve indulged. Aside from intermittent giggling, a dopey smile, and a raging appetite, red eyes are one of the most obvious clues that someone has inhaled THC.

Having eyes as red as roses while sitting around with your smoking buddies is no big deal. However, strolling into work or public settings with bright red eyes can easily give the game away. Therefore, smokers should be familiar with a few strategies to conceal their altered state of consciousness. Continue reading to find out why weed makes your eyes red in the first place, how to get rid of red eyes, and how to prevent them from occurring to begin with.

What Causes Red or Bloodshot Eyes?

Of course, your eyes can turn red for reasons other than inhaling cannabis. Several associated symptoms can arise when the eyes turn red and you’re stone sober, including soreness, itchiness, watery eyes, and twitching. These symptoms are often caused by conditions such as:

  • Dry eyes
  • Conjunctivitis
  • Burst blood vessels
  • Blepharitis
  • Ingrown eyelash
  • Eyelid problems

The eyes can also become bloodshot for other reasons, such as drinking too much booze, staying awake all night, and reading in poor light conditions. The term “bloodshot” simply refers to the reddening of the whites of the eyes due to irritation or rupturing of the blood vessels.

However, none of these mechanisms explain why cannabis specifically makes the eyes red.

Why Does Cannabis Cause Red Eyes?

Cannabis causes the eyes to turn red for two primary reasons. One mechanism involves systemic changes, and the other involves external irritation.

Cannabis Lowers Blood Pressure

Cannabis strains containing moderate to high levels of THC appear to cause a slight drop in blood pressure [1] . This shift prompts the blood vessels and capillaries to dilate, in turn causing them to widen and allow more blood to pass through. After smoking weed, the small blood vessels in the eyes widen and deliver more blood into the eyes, making them appear red.

This mechanism also underpins the potential positive effects of cannabis [2] on conditions such as glaucoma—a pathology characterised by high levels of pressure within the eye. The vasodilation that occurs after smoking weed appears to reduce pressure within the eye.

Smoke Can Irritate the Eyes

Cannabis can also redden the eyes via irritation. Every smoker has experienced the misfortune of taking a plume of smoke to the eye at some point. This unpleasant sensation causes stinging and watering; however, this type of reddening usually clears up within a few minutes. In contrast, the other form of redness only resolves after the effects of THC begin to wear off.

How to Get Rid of Red Eyes

There are numerous strategies cannabis users can employ to reduce eye redness. Whether you’re on the way to a family gathering or couldn’t resist firing up a joint on your lunch break, use the tips below to conceal your high.

Eye Drops

In the modern era of cannabis, companies have developed products specifically to remedy the issue of red, bloodshot eyes. Cooling eye drops help to reverse the mechanism that underpins red eyes in the first place, and they do so very quickly. Apply drops according to the product instructions to return your eyes closer to their normal state.

Stay Hydrated

Keeping yourself topped up with water will help alleviate any dryness that accompanies your red eyes, possibly taking the edge off their newfound colour.

Throw on Some Sunglasses

If the two previous methods aren’t working, slap on some sunglasses as a last resort. Of course, how out-of-place this appears will vary greatly depending on the location and situation. If you’re meeting family for lunch under the Cali sun, you’ll get away with it. If you live under the grey skies of the UK and are catching up with your gran for dinner, you might look even more suspicious wearing them.

How to Prevent Red Eyes From Cannabis

Treating red eyes does work in some cases, but sometimes the stoned glow just can’t be contained. If you experience particularly extreme red eyes, you’ll want to focus on preventing the look as opposed to treating it. Use the tips below to avoid red eyes in the first place.

Smoke Low-THC Strains

If you’re in the mood for a smoke but have somewhere to be, consider smoking low-THC weed. Cannabis low in THC and high in CBD still offers an enjoyable and clear-headed effect, just without the glaring red eyes.

Eat, Vape, or Drink Your Cannabis

There are plenty of different ways to consume weed. Choosing an option that doesn’t carry the risk of introducing smoke into your eyes will help you avoid excessive redness caused by this irritating phenomenon. Do note, however, that these other forms will still cause red eyes due to systemic changes.

Are Red Eyes Dangerous?

No. The mechanism that underpins red eyes won’t hurt you. In fact, it might help you if you experience intraocular pressure. However, red eyes might get you into trouble in a different way. If you can’t risk getting caught high, red eyes can land you in a situation you’d rather not be in. Use the tips mentioned above to manage red eyes while enjoying cannabis whenever you so choose.

Ever wondered why your eyes appear red after smoking weed? Discover the science that underpins this phenomenon, and learn how to treat and prevent it.

Why does weed make your eyes red?

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  1. Under pressure: lower blood pressure and dilated capillaries
  2. Do edibles make your eyes red?
  3. 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

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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.

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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.