If I'm guessing correctly, the Parkers family is probably using this 'Dragon Blood' to activate the Dragon Blood Battle Form, achieving that semi-dragon transformation. Wang Teng speculated.
This method seemed powerful, but it carried certain risks. A slight misstep could lead to being overtaken by the wild beast consciousness within, making it impossible to return to human form.
The reason Landon became irritable and aggressive after using the semi-dragon transformation was because of the influence of this dragon's blood.
What use does this dragon's blood have for me? Wang Teng absentmindedly stroked his chin, unable to think of its immediate utility. He certainly didn't want to end up looking like Landon did earlier, as that appearance was quite unattractive.
He didn't like it.