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.
One of the many ways that THC (tetrahydrocannabinol) affects us is by decreasing our blood pressure. And one of the effects of decreased blood pressure is the expansion of our blood vessels (which include arteries, veins, and capillaries).
The reason behind the redness is actually THC.
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 redness of the sclera (also known as the white of the eye) is a completely non-dangerous side effect of cannabis consumption, so if you’ve found this article to check if you’re in any immediate danger do not fret, everything is quite alright ;-).