Why Does Cannabis Make Your Eyes Red? A Scientific Explanation
Using cannabis often results in red, glassy eyes, which many people associate with smoke irritation.
However, the real reason lies in vasodilation, or the widening of blood vessels, rather than smoke exposure or dry eyes. This phenomenon is caused by THC (tetrahydrocannabinol), one of over 113 cannabinoids found in cannabis.
How Does THC Affect Your Eyes?
THC interacts with cannabinoid receptors in the body, including those in the eyes. When THC binds to these receptors, it causes blood vessels to expand, increasing blood flow and lowering overall blood pressure. This increased blood flow to the eyes is the primary reason for redness.
Additionally, the drop in blood pressure can lead to mild dizziness or lightheadedness, particularly in individuals who naturally have lower blood pressure. Therefore, red eyes are not just a superficial effect but an indication of how cannabinoids influence the body’s circulatory system.
Is Smoke the Only Cause of Red Eyes?
It was previously believed that cannabis-induced eye redness was due to smoke irritation, but this is not the case. Even when cannabis is consumed through alternative methods—such as edibles or oils—eye redness can still occur. This confirms that the effect is due to THC’s impact on blood vessels rather than direct exposure to smoke or irritation.
What Else Do Red Eyes Indicate?
Understanding the science behind red eyes highlights how extensively cannabinoids affect the human body. In addition to making eyes red, cannabinoids influence blood pressure, heart rate, and other physiological functions. This also explains why THC has been researched as a potential treatment for glaucoma—since reducing intraocular pressure is a key aspect of managing the disease.
How to Reduce Red Eyes After Cannabis Use?
While red eyes are harmless, they can be uncomfortable or undesirable. Here are some ways to reduce them:
- Use eye drops specifically designed to constrict blood vessels and keep your eyes moisturized.
- Stay hydrated by drinking water to maintain overall eye moisture.
- Consume caffeine, as it can help constrict blood vessels and reduce redness.
- Rest and wait it out, allowing your body to fully metabolize the cannabis.
Conclusion
The redness in your eyes after consuming cannabis is directly linked to THC’s effect on blood vessels, not to smoke irritation. When THC binds to cannabinoid receptors in the eyes, it causes blood vessels to dilate, increasing blood flow and creating the characteristic redness. This effect occurs regardless of the method of consumption, reinforcing that eye redness is not just a reaction to smoke.
While red eyes are generally harmless, they can be alleviated using methods such as eye drops, hydration, and caffeine consumption. This phenomenon further illustrates how cannabinoids interact with the body on multiple levels, extending beyond just the psychoactive “high.”
