For sample children, interviewers asked the broad opening question, "During the past 12 months, has [name] had any of the following conditions?," with hay fever as one of many conditions named. For sample children, the inquiry did not specify that the allergy had to be diagnosed by a doctor or other health professional.

For sample adults, the question was, "During the past 12 months, have you been told by a doctor or other health professional that you had hay fever?" The wording of this question may have led to an understated incidence of hay fever in adults. Adults who had received a diagnosis of hay fever from a physician during the past twelve months would certainly have responded affirmatively, but adults who suffered from an annual bout of hay fever and who had received the hay fever diagnosis from a physician in an earlier year could well have answered no under a literal interpretation of this question wording.

For sample children, for 1997 forward, information was also collected on whether, during the past 12 months, the child had respiratory allergies (RALLERGYR), food allergies (FALLERGYR), or skin allergies (SALLERGYR). In 2007 only, interviewers asked respondents if the sample child had any other allergies besides hay fever or respiratory, food, or skin allergies during the past 12 months (OTHALLERGYR).

In 2002, sample adults age 18+ were asked if they had ever been told by a doctor or health professional that they had an allergic reaction to medication (MALLERGYEV) or an allergic reaction to food or odors (FOALERGYEV). Respondents with an affirmative response to MALLERGYEV (Ever told had medication allergy) were asked if they had an allergic reaction to medication during the past 12 months (MALLERGYR). Respondents with an affirmative response to FOALERGYEV (Ever told had food/odor allergy) were asked if they had an allergic reaction to food or odors during the past 12 months (FOALERGYR).