Red eyes can also be caused by any number of other things, including : [substeps] Allergies illness (such as a common cold) lack of sleep recent crying irritants in the eyes excessive sun exposure [title] Watch for signs of dizziness. [step] Someone who has recently consumed marijuana may become dizzy or uncoordinated.
[header] How to tell if someone has been using marijuana [title] Look for bloodshot eyes. [step] Someone who has been using marijuana may have very red or bloodshot eyes. However, don't rely on this symptom alone as an indication of marijuana use.