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.

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

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!