Is it true that acne clearing chemicals and products are dangerous?

No: Life's a matter of weighing benefits and risks, and there's money to made by scaring people with quarter-truths about things they need. The acne treatments that actually work, from benzoyl peroxide to the vitamin a analogues and antibiotics, are well worth the (basically negligible) risks. If you're responsible for a young person's emotional & physical health, get them treated effectively.