What is a Hydrosol?
A hydrosol is produced during the steam distillation of plant material used to create an essential oil. One way to think of it as a flower water, but you can create a hydrosol from much more than flowers, so it's a bit of a misnomer. Hydrosols are basically essences of the material from which they are made.
I've been using the hydrosol step in my own skincare routine for as long as I can remember. The skin is most receptive to moisture and other skincare products when it is a bit damp. Using a face mist before applying your other serums and oils can help drive them deeper into the skin. The water acts as a vehicle for the other ingredients you add on top. One example I love to give is to think of two kitchen sponges: one being completely bone dry, and one being slightly damp. If you throw both into a bowl of water, the dry sponge will expand one corner at a time, or one uneven section at a time until it fully absorbs the water, whereas the damp sponge will expand much more smoothly and evenly. Another example would be to think of priming a wall before painting. Sure you can skip the primer, but you'll get a much more even finish if you take that extra step. For me, hydrosol is a necessary step, even in my decidedly minimal skincare routine.
I use my hydrosols daily before applying any other skincare to my face. The gentle spritz provides an uplifting feeling to my skin, a mini-reset. You can also use them to mist on top of makeup to add a little dew, or spray onto a cotton round to use as a traditional toner. Since they contain no oil, be careful with spritzing on dry skin alone repeatedly as this can lead to evaporation and dehydration. They are most effective when followed up with other products.