Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
allergy – n. a medical condition that causes someone to become sick after eating, touching, or breathing something that is harmless to most people
tick – n. a small insect that sucks the blood of animals
hysteria – n. extreme fear, excitement or anger which cannot be controlled
vast – adj. extremely large
symptom – n. a change that shows that a disease is present
