Is it permissible to perform tayammum instead of wudu' when suffering from a migraine accompanied by demonstrable harm?

Tayammum is a legal dispensation used when one is unable to use water. Therefore, if someone has a migraine or similar condition and is able to use water by heating it or performing ablution in a warm place, then ablution is obligatory upon him. However, if he fears that using water, even after taking supportive measures, will worsen his illness, delay his recovery, or cause another illness, then tayammum is permissible for him.