Is applying kohl to thin hair to conceal it considered a lie or an alteration of Allah's creation? Is it permissible to do so to alleviate psychological distress? And what is the impurity that invalidates ablution?

The remedies for obsessive thoughts are to completely ignore them, seek refuge in Allah from Satan, and recite the Quran. The strength of a Muslim lies in their steadfastness in their religion, not in their hair. One must remember Allah's blessings and be grateful for them. There is no harm in applying kohl to conceal the scalp if there is a need for it, and this is not considered changing Allah's creation, unless it involves imitating women or disbelievers. It is permissible to wipe over the head during ablution when kohl or henna are present, because wiping is based on ease and does not require water to reach every strand of hair.