Probably the hydrogenated vegetable oils and high glycemic index of potatoes. What you can do as a parent, is make sure potato chips don't come in the house. Hand make some sweet potato homemade chips. And control what goes on the table as best as possible making sure to be healthy and balanced. This will allow for healthy hormonal changes in your child's growing body and thus a "lessened" chance of acne.
First of all, don't react so severely to just 1 pimple. You could potentially be causing your child self-esteem issues.
Although I do think it's best to remove junk food from your child's diet, you don't want to do it in a manner that will cause them to rebel. I wish you luck. It's good that you're nipping this in the bud early.
What steps should a parent take for a child who is going to be reaching puberty in a few years. My child ate a whole lot of potatoe chips and got a large pimple. I said that's it! You have to be careful from now on. But I don't want her/him to get paranoid either.
why do you think chips are neccesarily bad or caused your son's large pimple,think about it,if he ate sprouts with his meals instead of crisps,then would he be spot free,
I discovered some 30 years ago my intolerance/allergy after suffering week in week out with a large pimple