VAS is an abbreviation for 'visual analogue scale' patients grade their symptoms along a line or a line of buttons, eg 1-10, where one end represents the worst and the other end the best scenario.
Visual analogue scales (VAS): Measuring instruments for the documentation of symptoms and therapy monitoring in cases of allergic rhinitis in everyday health care. Klimek L et al. Allergo J Int. 2017; 26(1): 16–24.