If you have become sensitized to an allergen, even an extremely small amount of the allergen in your environment can trigger an attack.如果对某种过敏原敏感，那么即便是生活环境中极微量的这种过敏原也能引起过敏。The daily pollen count can give a good indication of the amount of allergens in the air.每日花粉指数可以很好地反映出空气中过敏原有多少。