What foods are known to be related to acne (even if only in some people)?

Sweets,milk,seaweed: Studies show sugar, milk and high iodine foods like seaweed cause acne.

Milk: The only study worth a look was published recently from italy, showing a very small influence of milk. As a practical approach, diet is not a useful treatment for acne. There are several different remedies which are quite effective. If you have significant acne, don't bother with trivial things: a dermatologist can help you.