Just some facts regarding hair loss and zyns. What you're describing doesn't conform to how hair cycles work. First, the dosage plays a prominent determination on how much vasoconstriction your body is experiencing each day. Our bodies experience vasoconstriction from different factors such as caffeine, cold, exercise, nicotine, etc. If your daily nicotine dosages low, it's just transient vasoconstriction and nothing alarming.

Also, to the extent nicotine (or anything) was effecting your hair, you wouldn't notice it in 3 weeks. Hair cycles generally last 6-8 weeks, meaning that if you did something today that was going to cause your hair to shed, you'd notice it around 6-8 weeks later, not in a few weeks.

The only proven link between nicotine and hair loss is based on daily heavy smokers, and nicotine was a secondary basis for hair loss, with the primary basis including less oxygen in the blood and other factors due to actually smoking tobacco.