Why Does Marijuana Cause Red Eyes?

As more and more patients turn to a natural, alternative treatment options, it’s important that we continue to educate both those new and familiar with medical marijuana. At Mary and Main, we believe in cannabis education in efforts to end the marijuana stigma and help patients find relief. This week, we are turning our focus on how cannabis reacts with our bodies. While treating ailments and illnesses with medical marijuana, you may have noticed your eyes to become bloodshot after consuming the cannabis. Why does marijuana cause red eyes? There are a number of factors that may cause red eyes after consuming marijuana. 

What Causes Red Eyes After Smoking Cannabis?

The main reason you may experience red eyes after consuming medical marijuana is due to THC lowering blood pressure, causing blood vessels and capillaries to dilate. When the capillaries in our eyes dilate, it increases the blood flow to the eyes and relieves pressure. Because of this, cannabis is known to help treat glaucoma

For glaucoma patients, the THC induced vasodilation of ocular capillaries also temporarily reduces intraocular pressure. High intraocular pressure is the main symptom of glaucoma and can contribute to optic nerve damage and vision loss. Therefore, reducing this pressure is a key priority of glaucoma treatment. One study, published in the Journal of the American Medical Association, reported that smoking marijuana reduced intraocular eye pressure by up to 30%.

Why Doesn’t It Always Happen?

Having red eyes after smoking isn’t always a guaranteed symptom. That’s because each strain of marijuana has a different concentration of THC. This is why someone may experience intensely red eyes after ingesting a high THC strain, but barely notice the difference after a low THC strain.

However, there’s more at play than just THC content. As you may have experienced yourself, the same cannabis strain can have different effects on different people. These varying effects are due to a number of individual factors, including gender, genetics, and overall health.

Whether a person experiences red eyes or not is primarily influenced by their blood pressure. For instance, people with high blood pressure need more THC to lower their blood pressure enough to cause intense bloodshot eyes. Although, those with naturally low blood pressure can quite easily experience terminator red eyes.

With that being said, people with allergies to marijuana or smoke, in general, can experience exacerbated symptoms. But for users with an allergy, typically, red eyes are the least of their concerns.

Can I Get Rid of Red Eyes from Smoking Cannabis?

Experiencing red eyes as a result from consuming medical marijuana is harmless. However, if you prefer to reduce the redness, there are simple steps you can take! 

  • Consider a strain with lower THC
  • Use eye drops that are formulated to reduce red eyes  
  • Stay hydrated 
  • Plan your smoking time when you are in the comfort of your home 

How Can I Prevent Red Eyes?

One way to prevent red eyes is to choose a low THC strain or CBD. Since THC is the main cannabinoid responsible for red eyes, opting for a low THC strain or using CBD only will minimize the unwanted side effect. Of course, you won’t experience the same psychoactive effects, although high-CBD strains are ideal for days you don’t want red eyes.

The next best form of prevention is planning and time management. If you need to use marijuana before work or an important meeting, plan to do so well in advance to allow your body and eyes time to recover.



Mary and Main is a fully licensed and certified medical marijuana dispensary located in Capitol Heights, Maryland. Founded by doctors and experienced caregivers, Mary and Main provides safe, premium quality medical cannabis products with exemplary and compassionate service to all certified patients who are suffering from a number of chronic debilitating illnesses. 

Consult with our staff professionals to determine the best opiate-free, addiction-free treatment plan for your needs.