Yeah, the redness in our eyes is really uncomfortable. The time the redness lasts will depend on how much do you smoke. On other hand, if you just smoke one joint, the redness will only last for about one hour. If you smoked too much, the redness will disappear in some hours. Of course, it does not disappear for a long time and you are really worried about it, you can have a try with visine which will help you clear the dry eyes. Then, as the reasons why our eyes become red, in fact, there is another name of the redness called bloodshot. I think you know there is some marijuana in the smoke. The marijuana will increase the pulse rate, blood pressure, and heartbeat. As we all know, the increase of the blood pressure is the main reason why the eyes because bloodshot, then here will be some redness in your eyes.
If your eyes appear red after the smoking, it totally means that you are sensitive to the smoking smell. The irritating stimulations in the cigarettes come through your eye nerves. You'd better stop smoking and keep away from the spicy food. The red symptom may be lasted for about one or two days if you stop smoking and take care of your eyes.
How long will your eyes stay red after smoking? That will depend on your own condition of your body health. The better eyes health condition, the sooner recover of your eyes. The smoking will do harm to your health, and it will lead to various kinds of diseases, such as optic neuropathy, decrease of visual flexibility, macular degeneration, cataract etc. The nicotine will lead the decrease of choroid blood; the other dozens of harmful substances will remain in your body in a long term's smoking. That will reduce the absorbing of B12, as well as poisoning happen. Various toxins will stimulate, or damage the subtle tissues and structures within your eyes. If you have eyes disease, you would better get rid of smoking.
In fact, it is normal to get red eyes after smoking, because the smog which contains some toxins will give your eyes an acute sense. And because of that, your eyes will be affected and become bloodshot or something, actually, this is really bad. As to how long it will take for your eyes to recover, I gotta say, quite soon, if you don't smoke during the period and your eyes will be ok again, but you should also stop giving your eyes trouble.