While some people are misinformed about the relationship between oil and skin, others have tried serums but didn't use them correctly. You must apply on damp skin - that is, after you wash your face or after you apply toner. This allows for easy application and for the serum to be distributed evenly. The other reason why people are hesitant to try serums is because they seem to be expensive. If you use 4 drops a day and a 25ml container provides 500 drops, this means that one little jar will last 125 days or 4 months!