What a 1/5 rating means
On the comedogenic scale, a 1 sits at the safe end of the scale — clogging is unlikely for most people. That places Cyclomethicone in the range most people, including many with acne-prone skin, tolerate well.
One thing the number cannot tell you is concentration. Ingredients are listed in descending order, so Cyclomethicone near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About Cyclomethicone
It is a silicone, used to smooth, blur, and give a soft-focus finish. A volatile silicone that evaporates after application, leaving a silky feel. Low-risk at 1/5 and fungal-acne safe.
On a label it can read as Cyclomethicone, Cyclopentasiloxane, Cyclohexasiloxane — worth knowing when you scan an ingredient deck.
Cyclomethicone in makeup and skincare
It is everywhere in primers, foundations, and 'blurring' complexion products, and in serums and moisturisers. Its irritancy is rated separately at 0/5, which is low.