There have been numerous studies looking at the connection between acne and peanuts. First, though, let's cover how acne forms for those of you who may not know:
There's a bacteria that lives on your skin called Propionibacterium acnes. The bacteria basically feeds off your sebum, which is an oily substance secreted by the sebaceous glands in your skin. If your body makes too much sebum (your skin becomes too oily), these bacteria grow rapidly and your body must react by bringing in white blood cells to get rid of the bacteria. It's your own body's reaction which causes the inflammation that can lead to the red bumps, pain, and pus formation.
Many acne treatments, therefore, claim to help reduce oily skin (sebum) through various means (although most of them are ineffective). That is probably why peanuts are known to contribute to acne breakouts, because peanuts contain androgen hormones which can increase sebum production and oily skin.
Some of the studies regarding peanuts and acne have found that eating peanuts creates acne breakouts, while other studies have found no connections. Most of the studies were not actually done specifically to determine the connection between acne and peanuts, but rather between acne and a variety of foods such as chocolate, milk, cola, peanuts, and others.
What we do know, however, from many anecdotes is that some people do tend to have serious acne breakouts a few days after eating peanuts and that when they stopped eating peanuts, the acne went away. So it seems that, for some people at least, either an allergy to peanuts or a hormonal imbalance causes acne breakouts when they eat peanuts.
The theory behind peanuts contributing to acne breakouts is that peanuts (and milk too) contain androgen hormones which cause your body to create more oil (sebum). This excess oil along with clogged pores can contribute to acne breakouts. It's important to note that peanuts are not the cause of acne, but they may just make your existing acne problem much worse.
That's why we recommend anyone who is suffering from acne breakouts avoid peanuts for at least 30 days and see if it makes a difference.
We also recommend eliminating milk from your diet as there are strong connections between milk and acne, due to the hormones found in milk. For me personally, when I stopped eating peanut butter, cut milk out of my diet, and started eating more fresh fruits and vegetables for the fiber and antioxidants, my acne cleared up rather quickly.