Several recent studies suggest cutting back on dairy may help with teenage acne. Teenagers who drank 2 or more glasses (8 ounce servings) of milk were 20% more likely to develop acne. The fat content of milk does not appear to be related to acne development since the strongest link was found with those drinking skim milk; teenagers who consumed more than 2 glasses of skim milk per day were 44% more likely to develop acne.

Acne is a well known side-effect of steroid use in athletes and body builders, so it is possible that the sex and growth hormones found in milk are a possible acne trigger. For instance, blood levels of Insulin Growth Factor 1 (IGF-1), one of many growth-promoting hormones found in milk, peak in the adolescent years along with the incidence of acne. Bovine somatotropin (BST), also known as recombinant bovine growth hormone (rBGH) used to stimulate greater milk production from cows, increases the concentration of IGF-1 in milk perhaps contributing to acne development.

So why may skim be worse than whole milk for acne?  The whey protein milk processors add to skim and low fat milk to improve consistency, may be the reason. Whey may heighten the hormonal effect of milk directly, since it has steroid-like effects which help build muscle and increase exercise tolerance, and as a transport molecule for other hormones in milk.