Is it permissible to trim the beard when suffering from severe itching and sensitivity due to dry skin and the coarseness of the beard hair, knowing the religious ruling that it is obligatory to let it grow?

It is not permissible to shave the beard, but it is permissible to trim from it what exceeds a fist-full in normal circumstances. However, if a person is harmed by keeping it, then it is permissible for him to shave it or trim from it to the extent that necessity dictates, because "necessities permit the forbidden." What the questioner mentioned about his situation is considered an urgent need that permits him to lighten his beard hair to the extent that removes the harm, based on the ruling of shaving the head for a pilgrim in a state of ihram when there is harm. The principle is that it is not permissible to shave the beard or trim from what is less than a fist-full, but necessities like illness permit that, and the necessity must be estimated according to its measure.