Medically Reviewed by
Jason Crawford

Article Last Updated on January 11, 2023

Cannabis consumption can have a lot of side effects, some of which are somewhat serious, while others are nothing to be concerned about. Red eyes from weed is probably the least serious effect, but for some users who want to keep cannabis consumption a private affair, it’s one of the least desired ones.

Eye redness is a side effect that all cannabis users will experience sooner or later. While it isn’t at all dangerous, it’s understandable why some want to avoid it. For that reason, we’ll give you all the information on eye redness, why it happens, and how you can get rid of it, so read on.

Why Do You Have Red Eyes After Smoking Weed?

While some people believe that you only get red eyes when smoking joints, bongs, or blunts, the truth is that you can also get red eyes from consuming edibles, dabbing, and even vaping. So the smoke is not the cause, but the weed itself.

The redness which appears in the sclera (the white of the eyes), often called bloodshot eyes, isn’t dangerous at all. It doesn’t happen because your eyes get irritated, but rather from the cannabinoids in weed, mainly tetrahydrocannabinol (THC). The amount of THC and CBD in the cannabis strain is also important since strains higher in CBD but lower in THC don’t give such intense red eyes.

After weed consumption, THC binds to the cannabinoid receptors and decreases the blood pressure, which causes blood vessels and ocular capillaries to dilate. The dilation increases the blood flow in the eyes and reduces the intraocular pressure, and the increased blood flow leads to the reddening of the sclera. This is why the effect is called “bloodshot eyes,” because the blood literally shoots up in the eyes.

Some users wonder whether all cannabis products make the eyes red, and the answer is – yes. Since all cannabis products, including edibles, tinctures, vapes, dabs, and others, contain THC, they all cause you to have red eyes due to vasodilatation.

THC and Intraocular Pressure

By reducing blood pressure in the body, THC also reduces the intraocular pressure of the eye. Increased levels of intraocular pressure are common causes for glaucoma diseases, which can cause a severe loss of vision and even blindness. Therefore, by lowering the intraocular pressure, one can fight against glaucoma.

Cannabis and Glaucoma

The reason why cannabis causes bloodshot eyes is also a reason why cannabis is a great treatment option for glaucoma. This has been researched even back in the 1970s when scientists found that high THC strains can lower the intraocular pressure between 25% and 30%. That was the start of the research for the medical use of cannabis in the treatment of glaucoma.

However, to successfully treat glaucoma with cannabis and to maintain proper eye function, users need to have their intraocular pressure constantly lowered. The best cannabinoid products for treating this condition are oral cannabis solutions like oils, capsules, and edibles since their effects are longer-lasting compared to smoking marijuana in a joint. 

Does Every Cannabis User Get Red Eyes?

There is no one-answer-fits-all when it comes to the effects of cannabis on people who consume cannabis on a regular basis. That’s because the effects of weed can vary depending on genetics, overall health, sex, and how often you consume cannabis since regular use can increase cannabinoid tolerance.

This is also the case when it comes to bloodshot eyes. Some people get intense effects, while others won’t experience this side effect at all. The red eyes also depend on your blood pressure. For people with high blood pressure, THC won’t decrease the pressure enough to cause red eyes. 

However, for people with low blood pressure who consume high THC strains, this effect can be heightened. Moreover, people with low blood pressure can even experience weakness in the legs and feel faint since the cannabinoids will lower the blood pressure significantly. So, adapting your dose according to your tolerance levels and your personal health conditions is essential if you want to have a pleasant marijuana experience.

Marijuana Allergy and Red Eyes

Bloodshot eyes can also occur in people who are sensitive to smoke. Moreover, people with a cannabis allergy can experience even worse symptoms than red eyes.

The manifestations of the cannabis allergy depend on how someone was exposed. For example, contact with the plant can cause hives, rashes, or swelling. Meanwhile, breathing or inhaling marijuana results in ocular allergy symptoms, and other side effects.

Getting Rid of Red Eyes After Smoking Weed With Eye Drops

Users often want to diminish this telltale sign that alludes to them consuming cannabis, and here’s what you can do in those situations. Keep in mind that if you have high blood pressure, this side effect won’t be as bad, though if you have low blood pressure, opting for low THC strains may be a better option.

The best way to reduce this effect is by purchasing some over-the-counter eye drops such as Visine which are used for allergies, itchiness, and redness. They often contain tetryzoline (tetrahydrozoline) – an alpha-agonist that constricts dilated blood vessels. Since THC dilates the blood vessels and capillaries, the eye drops reverse these effects.

If you aren’t a fan of eye drops, you can use other alternatives that constrict the blood vessels which include chocolate, caffeine, licorice, and sodium, which is a great idea if you’re also experiencing the munchies. 

One misconception related to red eyes is that the side effects are caused by a lack of hydration, though that isn’t true. While dry mouth is also a side effect of cannabis use and is improved with adequate hydration, red eyes can’t be fixed with drinking water. 

Final Thoughts on Cannabis Causing Red Eyes

Next time you purchase your favorite cannabis strain from your local dispensary to use in your next weed session, think about purchasing some eye drops to get your eyes back to their natural state. And if you want to avoid getting red eyes altogether, high CBD strains may be a good option for you since they won’t only prevent you from experiencing such intense red-eye effects, but they’ll also give you more sedative effects.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.