Explanation:
People yield to quackery in times of great stress, pain, or sorrow. In the absence of exact knowledge, and sometimes even in its presence in the face of insurmountable difficulties, the credulous person craves a miracle and is ready to be overwhelmed by the personality and the claims of the charlatan.
The conditions usually treated by quacks are those for which specific methods of treatment have not yet been developed; those particularly feared, such as cancer, sexually transmitted diseases, and, in the past, tuberculosis; those with frequent remissions and recurrences, such as arthritis, neuritis, and migraine; and mental disorders.
