The most direct route is a simple explanation that we have a chronic pain condition which is greatly affected by certain factors, followed by a polite request. If your request is granted, make sure to express your appreciation. The way we ask makes a difference. In the United States, helping others is considered an act of charity, not something expected of us. But if we focus instead on how much we appreciate their assistance, others will likely oblige.
Many people have strong preferences.
Because many aspects of daily interactions create additional difficulties for us, it is completely reasonable to try to influence the environment to suit us better. But while our condition may be severe, everyone has preferences and people vary in their flexibility. It is unrealistic to assume we alone experience ailments. When asking for help, show respect for others and inquire about how the change may affect them. Many people, for example, suffer from back trouble.