Hives caused by stroking the skin (often linear in appearance) are due to a benign condition called dermatographic urticaria.

Dermatographic urticaria (also known as dermatographism or "skin writing") is marked by the appearance of weals or welts on the skin as a result of scratching or firm stroking of the skin.

Dermatographic urticaria (also known as dermographism, dermatographism or "skin writing") 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.