Historical clue formulations

• Milk sugar — 2023-09-05
• Many people find it intolerable — 2022-04-03
• ___ intolerance — 2018-02-04
• Source of some intolerance — 2012-09-30
• Cause of some intolerance — 2003-09-21
• Source of intolerance — 1999-04-29
• What some folks can't tolerate — 1997-12-31