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Why Does Weed Make Your Eyes Red?

Its 2am, your smoking buddy has passed out, you go to the bathroom and look in the mirror and see you have really red eyes. Although it differs depending on the individual, the type of weed and the circumstances, sooner or later most regular cannabis smokers will see a reflection of themselves and wonder if they hit that last joint a bit too hard. 

The redness may clear up rather quickly, but most people are unaware of what causes these tell-tale stoner eyes. 

As can be expected, the reasons that somebody may experience this is down to a number of factors that influence everything from its severity and duration, to whether they will get red eyes at all. One thing that should be recognised, however, is that there is nothing abnormal or dangerous about the phenomenon, and it should not be seen as something that suggests a bigger problem.  

Why weed makes your eyes get red?

The actual cause of red eyes is what makes marijuana so fun in the first place – the THC (tetrahydrocannabinol) content. This is the component of the cannabis plant that makes you feel high, but it also has a number of other effects on the body. One of those things is a lowering of blood pressure, which consequently makes your blood vessels dilate. This means that when you smoke, the capillaries in your eyes will experience an increase in blood flow and circulation, while simultaneously having a reduction in intraocular pressure. As the blood vessels expand they appear as irritation against the whites of the eye, resulting in this infamous effect. 

This therefore means that high THC strains pack more of that red-eye factor. In short the redder the eyes, the higher the THC you’ve just taken into your body. This remains true whether you have smoked your weed, vaped it or ingested it in edibles – you’re still getting those stoner eyes.  

One exception to the fact that THC causes red eyes is when the bloodshot effect happens as a result of being allergic to cannabis or the smoke itself. In the latter case, however, the individual would be sure to get red eyes even if they were exposed to smoke in any other situation, whether this is from weed, cigarettes, a bonfire, or even incense. 

why does weed make your eyes red

Always quick to point out the positives in any weed-related situation, all stoners in the know will tell you how those bloodshot peepers are indicative of another one of marijuana’s benefits, namely its effectiveness in treating glaucoma. Glaucoma is an eye condition caused by a build-up of fluid inside the eye, leading to the individual sustaining damage to their optic nerve if left untreated. Optic nerve damage means sight loss, making glaucoma potentially serious condition. 

The THC-fuelled drop in blood pressure that cannabis gives a user can also mean a reduction in pressure on the optic nerve. This is due to the dilation of the ocular capillaries, allowing more blood into the eyes. This may create redness but it also reduces the pressure in the eye itself, meaning less damage to your vision. Yet this is not a perfect solution as pressure to the eye is not the only cause of glaucoma, and even so it may take frequent consumption of weed to manage it this way. True, this may sound like a fun problem to contend with, but the realities of life mean it is not always convenient to be stoned. 

While most people will experience red eyes if you simply get enough THC in their bodies, there will of course always be those people with the kind of genetic makeup that makes them perfect stealth-stoners. These people will simply never experience red eyes regardless of their strain’s THC content. For the rest of us mere mortals, however, there are a number of options available to reduce the chances of getting those dreaded red eyes, or to handle them if they have already paid you a visit. Remember that even the worst case of bloody scleras will clear up in a couple of hours, but for those without the luxury of time here are a few things you can do to get away with it. 


Having your favourite sunglasses to hand can be a lifesaver if you need to rush out mid-redeye. The downsides? Certain circumstances make it impolite to speak with people without removing such eyewear, meaning your disguise will either be foiled or you will simply be choosing one social faux pas over another. Secondly, unless you live somewhere that is always warm and sunny you risk looking like a bad extra from The Matrix as you step out in your Wayfarers to an overcast rainy day. 

Choosing a low-THC strain 

Yes this is the least fun option but prevention is always better than the cure. You can’t have your cake and eat it too, so if you want to remain socially presentable while enjoying what cannabis has to offer then you’ll have to take a hit on the THC volume. As it is typically high-THC strains that leave users with those give-away eyes, selecting one with a more modest THC level may do the trick. 

Eye drops 

If sunglasses and less potent weed aren’t for you then a good bottle of eye drops could be what you need. Veteran smokers frequently recommend Rohto Cool or Rohto Cool Max as an expensive but effective way to clear things up, though warning should be given that they do tend to sting when used. Whether it’s worth the cost and discomfort will be for you to decide. 

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