weigh in. Be weighed; also, be of a particular weight. For example, Because it was such a small plane, the passengers and their luggage had to weigh in before takeoff , or The fish weighed in at 18 pounds. [Late 1800s] See also: weigh.
Asthma and allergic diseases, such as allergic rhinitis (hay fever), food allergy, and atopic dermatitis (eczema), are common for all age groups in the United States.
There are four types of hypersensitivity reaction, classified according to the way in which the ALLERGEN or ANTIGEN activates the reaction. The classic allergic reaction is the type I hypersensitivity reaction, with exposure to an external substance (the allergen) initiating the IMMUNE RESPONSE.