Why Does Cannabis Make Your Eyes Red?

We all know the feeling: you wake up after a long night of smoking cannabis and your eyes are bloodshot and red. But why does this happen?

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For many people, one of the tell-tale signs of cannabis use is red, bloodshot eyes. While bloodshot eyes can be a side effect of smoking any substance, including tobacco, the culprit for red eyes when smoking cannabis is actually the compound tetrahydrocannabinol (THC). THC is the main psychoactive component in cannabis, and it binds to receptors in the body that are responsible for regulating things like mood, appetite, and pain perception.

The Science Behind Red Eyes

When you smoke cannabis, the active ingredient THC binds to receptors in your brain. This alters your perception and can cause changes in your mood, thinking, and sense of time. It can also lead to short-term effects like difficulty concentrating, feeling dizzy, and bloodshot eyes. So, why does cannabis make your eyes red?

The Cannabinoids

Cannabis contains several different chemicals known as cannabinoids. These include THC (tetrahydrocannabinol) and CBD (cannabidiol).

THC is the main psychoactive compound in cannabis. It’s what gives you the “high” feeling. It also has some medical benefits, like relieving pain and reducing inflammation.

CBD is non-psychoactive, meaning it won’t make you high. It’s thought to have similar medical benefits to THC, but it’s not clear how it works.

Both THC and CBD can make your eyes red by increasing blood flow to them.

The Ocular Pressure

The ocular pressure is the pressure inside your eyes. It’s usually about 14 to 20 mmHg. But it can go up to 30 or 40 mmHg when you smoke cannabis.

The ocular pressure is higher in people who have glaucoma, a condition that damages the optic nerve. The optic nerve connects your eye to your brain.

Cannabis increases the ocular pressure because it narrows the blood vessels in your eyes. This is called vasoconstriction. It happens because cannabis has chemicals that mimic those in your body. These chemicals are called cannabinoids.

Cannabinoids attach to receptors in your body, including receptors in your eyes. When they attach to these receptors, they change how the cells work. This can include changes in cell growth, blood sugar levels, and inflammation.

The Myths

One of the most common questions people ask about cannabis is why it makes your eyes red. Unfortunately, there is no clear answer. Some people believe that it is because of the THC in cannabis, while others believe that it is because of the terpenes.

The Bloodshot Eyes

The bloodshot eyes are the most common symptom associated with cannabis use. It happens when the small blood vessels in the eye become dilated. This is caused by the active ingredient in cannabis, THC, which binds to receptors in the brain that regulate blood pressure and heart rate. When THC binds to these receptors, it causes a decrease in blood pressure and heart rate, which leads to the dilation of blood vessels. The dilation of blood vessels in the eye can cause redness, dryness, and irritation.

The Dilated Pupils

Dilated pupils are one of the most noticeable effects of marijuana. When you smoke, your body releases a chemical called acetylcholine, which is responsible for controlling the size of your pupils. The effect is temporary, and usually wears off within a few hours.

The Remedies

There are a few reasons why your eyes may turn red after consuming cannabis. It could be that you are sensitive to the smoke, or it could be that you are allergic to the weed. If you have been smoking weed for a while and your eyes are still red, it could be time to consult an eye doctor.

The Artificial Tears

The most common remedy for red eyes is to use artificial tears. These over-the-counter drops can help to lubricate the eyes and reduce irritation.

There are a few different types of artificial tears, and it’s important to choose one that’s right for you. If you have dry eyes, you may want to use a gel or ointment. These provide more relief but can also cause blurred vision.

If you wear contact lenses, you may need to use a different type of drop. Some contain preservatives that can build up on lenses and cause irritation. There are also preservative-free options available.

You may need to experiment with a few different types of artificial tears to find one that works best for you.

The Warm Compress

The warm compress is one of the most popular and effective home remedies for getting rid of red eyes. You can use a warm towel or a heating pad set on low. Place the warm compress over your eyes for a few minutes. The heat will help to soothe the blood vessels and reduce the inflammation.


It is not fully known why cannabis makes your eyes red, but it is thought to be related to the plant’s ability to dilate blood vessels. This dilation of blood vessels can also cause other symptoms such as dry mouth and increased heart rate. While the science behind this phenomenon is not fully understood, it is generally considered harmless and will wear off after a few hours. If you are concerned about your symptoms, please speak with a medical professional.

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