IntroductionAcne is just another word for spots. If you have severe acne, you get lots of spots, or spots that are large, red, and sore.
Most people don't like it when they get spots on their face. Acne can also affect other parts of your body. You can get it on your neck, chest, back, and arms.
Spots happen when you get a build up of natural oil under your skin. Small glands in your skin make an oily substance called sebum. This stops your skin drying out.
Sebum comes out onto the surface of your skin through tiny holes called pores.
If a pore becomes blocked, sebum can build up. This can cause several kinds of swellings or spots on your skin.
- If sebum builds up just under your skin, you get white bumps called whiteheads.
- Blocked pores can get quite wide and open up. This causes small dark marks called blackheads. The black bit is a plug of oily sebum and protein from your skin. It's not dirt.
- Spots can turn red and become inflamed. These are called papules. They happen if bacteria start growing in the sebum that's built up.
- Some inflamed spots contain pus. These are called pustules.
What causes acne?We don't know exactly what causes acne.
The main reason teenagers get acne is probably the change in hormones that happens when you reach puberty.  The change in hormones can cause your skin to make more sebum (oil). The extra sebum can make your skin greasy.
You're more likely to have acne if other people in your family have it.  And some kinds of oily make-up may block your pores and trigger acne. 
If you have acne, there are things that can make it worse: 
- Rubbing your skin
- Picking or squeezing your spots
- Tight clothes or bag straps that rub your skin
- Pollution and high humidity
- If you're female, the change in your hormones that happens when you have your periods, or when you start or stop taking the contraceptive pill.
Myths about acneThere are lots of myths about acne. Here are some common ones.  
- You might hear people say that you get acne when you don't wash enough. But this isn't true. Blackheads aren't black because of dirt. Hard scrubbing can make acne worse.
- A lot of people say that greasy foods cause acne. But there's no good evidence that fatty foods or chocolate cause acne for most people. Some research does suggest that eating a lot of energy-rich, low fibre foods could make acne worse.  That's probably because these foods release energy quickly, which could affect the balance of hormones in your body.
- Some people think that you can catch acne. Again, this isn't true. You can't catch acne or pass it on to someone else. Although acne is partly caused by bacteria, these live on your skin naturally and are usually harmless.
Inflammation is when your skin or some other part of your body becomes red, swollen, hot, and sore. Inflammation happens because your body is trying to protect you from germs, from something that's in your body and could harm you (like a splinter) or from things that cause allergies (these things are called allergens). Inflammation is one of the ways in which your body heals an infection or an injury.
Bacteria are tiny organisms. There are lots of different types. Some are harmful and can cause disease. But some bacteria live in your body without causing any harm.
Hormones are chemicals that are made in certain parts of the body. They travel through the bloodstream and have an effect on other parts of the body. For example, the female sex hormone oestrogen is made in a woman's ovaries. Oestrogen has many different effects on a woman's body. It makes the breasts grow at puberty and helps control periods. It is also needed to get pregnant.
Puberty is the time when boys and girls develop secondary sexual characteristics. For boys, the major changes include pubic hair, a deeper voice, and growth of their penis and testicles. For girls, major changes include pubic hair, breasts and starting to have periods. After puberty, girls are able to become pregnant and boys are able to father children.
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