Isoderm Soap Free pH5.5 Baby Liquid Cleanser 250ml Isoderm is non-alkaline and soap-free, sharing the normal pH value of healthy skin at 5.5. Conventional soaps, though effective, are alkaline in nature, and can interfere with the skins natural pH level. We need our skins natural acidic barrier to protect our skin against environmental factors and infections, so if our skin loses its acidic pH, it will become vulnerable to allergies and infections.