Well, it often happens to some people who keep smoking to have bloodshot eyes. As we know that by smoking, it can cause a complex interaction between your body and the same kind of chemical reaction that produces bruises. And in that way, it can make your blood pressure high. Then, this lead to high eye pressure. It results in your bloodshot eyes. So if you do not want to have the bloodshot eyes, you should quit smoking. If you keep smoking, it actually does harm to your health, not only the eyes, but also the body organs. As we know that by smoking, it can produce cyanide which is a retinal toxin. And according to some research, Smokers may develop toxic amblyopic problem. And also, it can degrade the night vision. So it can be kind of dangerous.
Bloodshot eyes is a condition that the whites of the eyes appear red. The reason of get bloodshot after smoking weed maybe because you are allergic by smoking. I suggest that you'd better see a doctor and have a allergy test.
For I know that bloodshot eyes can be caused by a variety of infections as follows:
1. Cold, when you're get a cold, that will be cause bloodshot eyes, especially viral respiratory infection.
2. Mild to serious allergic reactions can cause bloodshot eyes.
3. Wrong way of using contact lens can cause bloodshot eyes.
4. Eye injury or surgery also can cause bloodshot eyes.