Dermatographism

Dermatographic urticaria (also known as dermographism, dermatographism or "skin writing") 
It is a skin disorder seen in 4–5% of the population and is one of the most common types of urticaria, in which the skin becomes raised and inflamed when stroked, scratched, rubbed, and sometimes even slapped. It is most common in young adults, ages 20-30 during times of high stress or depression. (wikipedia)

This is Jay's arm. We tried if he'd demonstrate dermatographism because when I tried writing on my arm it didn't exhibit the same as in Jay's arm. Notice the elevated rash with reddened borders. He also said that it is itchy and he's just preventing himself from scratching it because it'LL ruin the name written on his arm. Anyway, you can try this by placing a deep scratch using your finger on your arm. If it becomes raised and inflamed like the one in the picture, you have dermatographism. If not and you just presented with a flat, not elevated reddened streak, you don't have this.