The causes of breakouts depend on the individual, and therefore to tailor the answers to you we will need to ask you a few questions.
Greasy / oily skincare products or excessive makeup: These can block pores (the openings of hair follicles) and trigger acne breakouts.
Occlusion: Mechanical blockage of hair follicles through occlusion with tight clothes or more recently masks can lead to acne breakouts. A change in hormonal contraception, for example stopping the combined oral contraceptive pill, changing to a new brand or starting progesterone only contraception can trigger an outbreak.
Corticosteroids: Topical steroids are widely used for the treatment of conditions such as eczema on the face. They can worsen acne and rosacea. Corticosteroids (e.g. prednisolone) are also prescribed in tablet form for the treatment of a wide range of conditions and can trigger outbreaks.
Testosterone and Anabolic steroids: Testosterone levels increase around puberty and this is a significant contributor to the acne flares that are seen at this age. Testosterone may also be prescribed medically for certain conditions and this can cause significant acne. Anabolic steroid hormones related to testosterone and are sometimes abused by athletes and body builders and can result in very severe acne flares.