Can you tell me how could an allergy test work?

Supports a history: -supports history. If a person gets sick at certain times of a year- a pos. Skin test to the appropriate seasonal allergen can help guide treatment and predict seasonal worsening. - helps guide allergy avoidance. If an asthmatic with repeated worsenings is test pos to cat, getting the cat off his chest at night can help. -guides allergy desensitization. Anaphylaxis to bees, decreasing sensitivity.