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Why do eyes get red from Cannabis?

why do eyes get red cannabis

One of the telltale signs that someone has used cannabis is red eyes.  Visine has made a fortune due to red eyes.  It is one of the 1st side effects that new cannabis smokers notice.  The question is why does this happen?

Although it can be a little irritating to have bloodshot eyes many people wonder if there is any actual damage being done to your eyes?  Is this just an allergic reaction?  Is it just the smoke that is irritating our eyes?   Well the truth is red eyes aren’t really any major health issues and no it isn’t actually an allergic reaction.

Science of Red Eyes

After taking a cannabis product a user will most likely have an increased heart rate and elevated blood pressure.  The reason this happens is because of the plants cannabinoids.  These are the building blocks of cannabis.   They are chemical compounds that are responsible for all the various effects.   The most known chemical compound in cannabis is THC.   It is the compound responsible for the “high” you feel.

One of the major effects of THC that produces this sensation is an increase in heart rate and therefore blood flow.  The increased blood flow is actually also responsible for a drop in overall blood pressure.  Blood flows to various capillaries in the body and causes them to dilate.  The eyes are one of the major centres of this increased blood flow.  This is know as vasodilation.

Once this initial spike occurs it take a bit of time for your heart rate to return to normal.  I’ve actually used my fitbit while high to measure this increased heart rate and have often noticed with very strong cannabis varieties my heart rate can essentially double from normal resting rate.  This often means my heart rate shoots up to roughly 120bpm.  This is the same as if you’ve been doing relatively brisk exercise.  It usually takes a bit of time for this increased heart rate to diminish.  This can be within 10 mins or a little over 30 mins depending on the strength of the cannabis.  This initial spike causes your blood pressure to lower.  As this happens it is your blood vessels and capillaries that dilate.   This includes the capillaries around your eyes.  This process causes increased blood flow to the eyes.  This is the reason your eyes start turning red.  It also reduces ocular pressure hence it being a remedy for those suffering from glaucoma.

Do edibles make your eyes red?

Well according to what we’ve just discovered above the short answer is yes.  The reason is because edibles are causing the same vasodilation.  The smoke really has nothing to do with your eyes becoming red.  Usually the amount of redness or lowered glassy eyes with correlate with the actual level of THC dosage.  Because smoking creates more of a rapid onset of the “high” it may cause red eyes much quicker than edibles do.  Edibles tend to take 60-90 mins to fully kick in and it is when that initial heart rate starts to decrease that the capillaries begin to dilate.

Does CBD make your eyes red?

Good question.  The interesting thing is that CBD actually does not make your eyes red at all.  This is because it has the opposite effect of THC in terms of pressure around the eyes.  CBD will actually increase pressure around the eyes.  The many various cannabinoids are responsible for so many different effects.  Due to this issue, it is not recommended for people with glaucoma to use heavy doses of CBD to treat their condition.  CBD can be great for inflammation, minor pain and anxiety but in this case it is actually not beneficial.

Whats the best way to alleviate red eyes?

There are a few ways people try to reduce their red eyes from consuming cannabis.  Primarily eye drops is the often go to quick fix for this issue.  Our little fact finding mission states that visine and clear eyes are the too most common brands that people use.  Visine has a specific redness relief formula.  Apparently their “max relief” drops are quite hard on the eyes and not really recommended by people that have tried it.  If you want a less expensive and more natural way to deal with the redness you can try just cold water.  Washing your eyes and face really well with cold water can often do the trick to diminishing the redness factor. It also helps to stay very well hydrated.  I think drinking ample water is basically just plain solid advice for life.   You could also take some pure CBD oil drops as that will counteract the effects of THC.