Why Weed Gives You Red Eyes (and How to Get Rid of Them)

Bloodshot or “red” eyes are one of the most familiar side effects of cannabis, and there are two main reasons it happens: THC lowers your blood pressure and dilates the capillaries in your eyes, and — less often — smoke simply irritates them. The effect is harmless and usually fades within a few hours.

Why does weed make your eyes red?

Cannabis lowers your blood pressure

The most likely explanation is also the reason cannabis is such an effective treatment for glaucoma: the THC in it lowers blood pressure and, as a result, makes blood vessels and capillaries dilate. Some of those dilated capillaries sit in the eyes — they're known as ocular capillaries. As THC enters your system, the ocular capillaries widen, allowing greater blood flow and giving the eyes that telltale reddish tint.

A possible allergy

A less common cause of red eyes after consuming cannabis is an allergy or irritation triggered by the plant or its smoke. In these cases, though, the redness isn't specific to cannabis at all — it's most likely a universal reaction to any kind of smoke or irritant that comes into contact with the eyes.

One key clarification: it's the cannabinoids themselves that redden your eyes, not the consumption method. No matter how THC gets into your system — smoking, edibles, whatever — if the dose is high enough, your eyes can turn red.

How to avoid red eyes when smoking

Completely avoiding red eyes can be next to impossible whether you smoke, vape or even use edibles — the biology is almost always the same. What can help is choosing a strain with less THC, which may have a milder effect on your eyes. It's a common misconception that the longer you've been smoking or the higher your tolerance, the less likely your eyes are to go red. 

The overall result varies depending on how quickly your body metabolizes the THC that reaches your bloodstream. Several factors affect that process, including age, health and individual sensitivity to THC. So there's no one-size-fits-all fix. The general consensus is that your eyes will likely stay bloodshot for about an hour or two after consuming cannabis — sometimes a bit longer.

How to get rid of red eyes from weed:

Eye drops for after you smoke

Hands down, eye drops are the easiest route to clearing your eyes after cannabis. Practically any over-the-counter redness-relief eye drops will do the job. Just be careful not to use them too often, as overuse can leave your eyes dry and irritated. And if you can, check with an eye doctor to find out which drops suit you best.

Cold compresses

Getting rid of post-smoke red eyes has another "fix": cold compresses on closed eyelids can sometimes help constrict the blood vessels so your eyes don't look quite so red.

Caffeine

Caffeine constricts blood vessels, so in theory it can help eyes reddened by smoking weed get back to normal afterwards. While there are no formal studies proving it, plenty of anecdotal reports claim that a cup of coffee or a caffeinated drink can help make the problem fade.

Sunglasses

Sunglasses probably won't make your weed eyes go away, but they can shield extra-sensitive eyes from the sun — and stop everyone else from noticing you look a little more tired, or more stoned, than usual.

How to prevent weed's effects on your eyes

Treating weed-red eyes doesn't always work — sometimes the high is so obvious there's no hiding it. If your eyes go red from cannabis, the smartest move is to prevent the look rather than treat it. Here are a few tips to apply right from the moment you start consuming:

Smoke low-THC strains

If you feel like smoking but want to dodge puffy weed eyes, go for cannabis low in THC. Low-THC, CBD-rich cannabis still delivers a pleasant, clear-headed effect — minus the glaring red eyes.

Eat, vape or drink your cannabis

There are lots of different ways to consume cannabis. Picking one that doesn't risk getting smoke in your eyes will help you avoid the extra redness caused by irritation. Keep in mind, though, that these methods will still redden your eyes due to the changes happening inside your body.

Is it dangerous to have red eyes from weed?

No. The mechanism behind red eyes after smoking weed isn't harmful. In fact, it could even help if you have elevated intraocular pressure. But red eyes can land you in a different kind of trouble.

The reason weed makes your eyes red can put you in situations that get tense. If you want to enjoy cannabis whenever you feel like it, lean on the tips above to keep the redness under control.

If you're a regular consumer — for medical reasons or otherwise — your body will eventually get used to this symptom, which is, after all, a phenomenon that should only be temporary.

However, if your eyes constantly and persistently turn red after cannabis and the redness just won't go away, there may be another cause — and you should book a medical appointment.

How long do red eyes from weed last?

Research conducted in the '70s and '80s showed an appreciable drop in intraocular pressure for three to four hours after smoking cannabis or ingesting THC.

So, going by that report, red eyes from weed should be an effect that lasts four hours at most.

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