How Long Does Weed Make Your Eyes Red

Why Do Your Eyes Get Red

Even though many people still believe that red eyes are caused by the smoke from a joint (or a blunt or a bong), this is completely untrue, because of no matter what type of consumption a person chooses, ranging from smoking, edibles, dabbing or vaping, the red eyes are gonna be there.

The reason behind the redness is actually THC.

One of the many ways that tetrahydrocannabinol affects us is by decreasing our blood pressure.

One of the effects of decreased blood pressure is the expansion of our blood vessels (which include arteries, veins and capillaries).

In the case of our eyes, the ocular capillaries become dilated and take in more blood, and the expanded blood vessels on the surface of the sclera make the eyes appear redder in color.

Tetrahydrocannabinol (by reducing blood pressure), also reduces the intraocular pressure of the eye. Increased intraocular pressure is the key for all glaucoma diseases, and lowering the IOP (intraocular pressure), is the only way for us to battle glaucoma, which when left untreated can result in a severe loss of vision, and ultimately blindness.

One of the first studies conducted on this correlation showed that high THC strains can lower the IOP in the range of 25% to 30%. 

The main issue with treating glaucoma with marijuana is that the IOP needs to be constantly lowered in order for the eye to function properly (oral solutions such as oils, capsules and edibles are best for this because of their extended duration), while the second issue is that the users who constantly consume large quantities of THC can experience some side effects in their everyday life.

The difference in people

If you and the people around you regularly consume cannabis, you probably already noticed that the same strain of weed has different effects on different people.

These differing effects happen because of a number of key factors which include genetics, sex, overall health and frequency of consumption (increased frequency causes cannabinoid tolerance).

You also might have noticed the same thing about the eyes. Some people get really intense bloodshot eyes, while on others the difference is barely visible, or even non-existent.

The redness is completely dependent on the person’s blood pressure. For instance, if you have high blood pressure, THC won’t be able to decrease it enough for your eyes to become super-red.

I actually have a completely opposite problem, as my blood pressure is rather low, so when I consume a potent THC strain, I literally look like the Terminator.

Besides the redness, when the session includes several joints/blunts I can also experience weakness in the legs and symptoms like feeling faint. This, of course, isn’t only a result of a low blood pressure but is brought about from a complex equation of factors I previously mentioned like age, sex, health, genetics etc.

Allergies can also play a factor in the overall “bloodshot volume”, as there are many people who are very sensitive to all smoke in general.

Another possibility for increased redness is cannabis allergy, but for users who have this unfortunate issue, red eyes are the least of their concerns. To find out more about this rare condition, click on the allergy link below.

We’ve now summed up the science behind the red eyes, so now I’ll be focusing on what we can do to diminish this telltale because sometimes we just don’t want everybody to know that we’re flying high.

The most common way to alleviate your red eyes is, of course, various over-the-counter eye drops that are designed for eye allergies, redness and itchiness.

Pretty much all variations contain tetryzoline (also known as tetrahydrozoline), which is an alpha-agonist that causes dilated blood vessels to constrict.

As I previously mentioned, THC makes our blood vessels and capillaries to dilate (directly causing the redness), so the eye drops reverse this effect and return our eyes to a normal state.

These types of medications are generally quite safe for use, but I strongly recommend that you always carefully read the manual that comes with the drops.

There are a few alternatives to eye drops which can also constrict the blood vessels in our body, such as caffeine, chocolate, liquorice and sodium.

A common misconception is that increased hydration can be used for reducing the redness of the eyes, which is entirely false.

People frequently perceive the redness as a sign of dehydration, because they associate it with the accompanying sensation of dry mouth.

One of the many ways cannabis influences us is by activating the endocannabinoid receptors that are found in our salivary glands. Once excited by cannabinoids from weed, they slow down the fabrication of saliva, which causes us to feel like there’s a desert where our mouth used to be.

Under pressure: lower blood pressure and dilated capillaries

After consuming a cannabis-based product (flower, concentrate, edible, etc.), users generally experience an increase in heart rate and blood pressure. This effect is due to the plant’s cannabinoids, which are chemical compounds responsible for some of the therapeutic and medicinal benefits of cannabis, and their initial interaction with the body. This rise in blood pressure and heart rate is comparable to normal physical activities like exercise or sex.

It generally takes about five to ten minutes for users’ heart rates to return to normal and for blood pressure to begin to decrease. As the blood pressure lowers, the blood vessels and capillaries dilate, including the ocular capillaries. The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red and also reduces intraocular pressure.

Evidence that the THC found in cannabis can lower intraocular pressure (IOP) is a major reason why many glaucoma patients have attempted to use medical marijuana to treat and relieve symptoms of the disease. It’s important to know that some studies have contradicted or added a caveat to the claim that cannabis is beneficial for glaucoma. For instance, a 2018 study conducted at Indiana University found that cannabidiol (CBD), the non-intoxicating cannabinoid found in marijuana, could potentially worsen the condition by increasing eye pressure. More research into the use of cannabis for glaucoma treatment is needed.