The Dermatest quality mark is a scientific quality mark for independently tested products that come into contact with the skin. If you want to buy safe and validated products, look for the Dermatest quality mark. The highest achievable quality mark is "EXCELLENT". Puratex® strong cleaner, Puratex® synthetic cleaner and the Puratex® microfibre cleaner all have the predicate "EXCELLENT". 

If you want to know how such a test works, look at this diagram: