Why Does Weed Causes Red Eyes?

Stephen Andrews
22 Aug 2022

It's one of the most conspicuous signs that you've had weed. The reason they crack your little secret and say, "Hey, Mike is high again. Did you see his eyes?" The war on red eyes is a real thing for many users. While such a reaction from consuming marijuana does not affect all users, others will freak at the sight of their bloodshot eyes every time they smoke pot, vape, or eat edibles.

You may wonder why cannabis consumption can sometimes result in red eyes. Biologically speaking, what happens when eyes turn red after weed is the same as why some people reach out for weed to treat glaucoma

Red eyes is a side effect of THC. The psychedelic compound lowers blood pressure in the body, affecting even the smallest capillaries throughout the ocular area. As ocular capillaries dilate because of weed, blood flow to the eyes increases, and there follows a drop in the intraocular pressure. 

The increase in blood flow is what creates reddening of the eyes, and while it may be irritating for some users, it's harmless. When it comes to glaucoma patients, what they aim for in treatment is the accompanying decrease in eye pressure. 

Do Red Eyes Occur Only When You Smoke?

Red eyes are the result of THC affecting the body, so it's not quite that the smoke makes your eyes red. When you ingest THC as a space cookie, tincture, or any other way, it may also cause reddening of the eyes. The stronger the strain, the more amplified this effect may be. 

Whether you are generally sensitive to smoke might be another story. It could be a cannabis allergy that subsequently contributes to more eye redness. However, an allergic reaction to smoke will also happen due to tobacco smoke or burning incense sticks. 

How to Stop Red Eyes?

Red eyes might be irritating and incredibly frustrating when you want to hide that you've consumed marijuana, however, it's pretty harmless and there are several things that you can do. You won't be able to stop it entirely, but you can minimize it. 

  • Use eye drops. There are many products, from "artificial tears" to unique formulas for red eyes, that can help cleanse the eye and reduce redness and itching. 
  • Drink plenty of water. This is a golden rule to follow when smoking pot. Dry eyes which can culminate in red eyes is a common side effect of weed. In general, marijuana augments sensations of dryness throughout the body, so the body demands more water to keep it healthy. 
  • Do nothing. After all, red eyes are not harmful. You don't have to do anything. If you notice that this is what brings you unwanted attention, you can put on sunglasses. Or when you know that red eyes might be a problem with some people, postpone the smoking session for that day for a little bit later. Until the moment is right and there's privacy to do it. 
Stephen Andrews