The link between diet and acne exists. Affected individuals often report acne worsening after drinking milk or after having chocolate and scientifically there is an explanation for this but this does not mean that you have a food allergy. Food with high glycaemic index (chocolate, sweets, pizza, cakes, fast food, fizzy drinks) is absorbed rapidly by the body which leads to increase the blood glucose (sugar) levels which in turn cause the release of insulin and insulin-like growth factors. Both of these are hormones which increase oil or sebum production by increasing the production of androgens (testosterone) in both men and women.
Another commonly known link is with dairy products. The scientific theory behind this is similar to mechanisms to diets rich in high glycaemic index mentioned above. Additionally, it has been suggested that milk from dairy cows either naturally contains growth hormones or is treated with growth hormones. Growth hormones increase androgen levels, which promote oil glands to release more sebum.
My advice to patients is to follow a healthy diet which is low in sugar and refined carbohydrates. Eat vegetables and fruit with a low glycaemic index along with fish high in omega 3 fatty acids. Avoiding processed food as much as possible. Keep a food diary for 12 weeks.
Another fascinating link has been found between in skimmed (low fat) milk and acne. It has been proposed that the process of removing fat from the milk removes some of its healthy components and higher oestrogen levels in skimmed milk.