Diet actually has very little influence on acne in most individuals. Very few people actually breakout from eating certain foods. The most common culprits are stress, genetics, cosmetics and certain medications. Pimples actually form as the result of dead skin cells and dirt (makeup) and bacteria mixing with the oils naturally produced by the skin. Occasionally, people do react to certain foods, but fish oil should actually have the opposite effect due to the antiinflammatory properties of the omega-3 fats. More than likely, the blemish in question occurred randomly, not as the result of your supplement. Would suggest trying the supplement again, if you notice a problem with your skin again, you may be one of the rare individuals with skin sensitive to diet. If you are not able to continue the supplement, would suggest trying to eat 2-3 3-ounce servings of fish each week to ensure you are getting the omega-3 fats that only fish can offer.