The negative factors are that it needs to be done frequently and the skin can suffer unless precautions are led.
Some people believe you need spiritual protection from dark spirits--that they can "get in". https://x2bysmjbdqslbjiea4vhyhmsi2gjkahdybcnztuhvrwu4kkmciqq.CDN.Ampproject.org/c/Cc.koreaapp.kr%2Fbbs%2Fboard.php%3Fbo_table%3Dfree%26wr_id%3D2660580