Acne is the result of access sebum production, clogged hair follicles from dirt, or a collection of bacteria. Sometimes stress is also said to be the cause. When the skin inflames and produces acne, then acne leaves blemishes that are hard to get rid of. The pigmentation of the spot increases and appears darker than the normal skin tone. Usage of products that help in reducing acne, like salicylic acid, or ingredients like tea tree oil which has anti-bacterial properties can help. The spots left behind can be diminished with ingredients like vitamin c, niacinamide, licorice extracts, etc.