Dear Ms. KnowBody,
My sister has no pimples at all, and I have them all over my face and it isn't fair. Why did this happen to me?
Heredity, or your family's experience with acne, has a strong influence on your chances of having it too. If your parents or siblings had acne, it is more likely that you will have inherited oily skin and an increased sensitivity to the effect of hormones. So, the reason you have acne and your sister doesn't is most likely due to the combination of genes you inherited from your parents. This means that you ended up with genes from one or both of your parents that caused you to have acne; whereas, your sister, got non-acne genes from both parents.
Knowing that your parents had acne when they were teenagers gives you an advantage -- you can be proactive and develop good skin care habits from an early age.
For more information on taking care of your skin check out Inside Out's article about zits!