What causes acne?
It afflicts millions of people each year, according to the American Academy of Dermatology.
But is it true that hormones and carbohydrate-filled foods really cause the biggest symptom of acne - pimples?
Hair follicles produce an oil known as sebum, which limits the amount of water entering our skin.
But when too much sebum is produced, it feeds a bacterium living in your skin known as Propionibacterium acnes, causing your immune system to flush blood and white blood cells to the area.
And if the follicle clogs up, a pimple forms.
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It's also thought carb-rich foods contribute to acne, as they increase a compound in your body known as insulin-like growth factor one, which turns up sebum production.
Androgens - a family of hormones including testosterone - also boost your body's sebum production, leading to more pimples.
Puberty and menstruation both cause significant hormonal changes, making teenagers prime candidates for acne and causing many women to break out around the time of their period.