There are many misconceptions and rumours about what causes the acne:

• Diet. Chocolate, potato chips and sugar, among others, have not been shown to affect acne. This means that the scientific studies done to date did not find a statistically significant difference between acne in two groups of people, one group eating the food in question and one group avoiding it. 

However, one recent study [1], based on a survey of 47,335 women, did find a positive epidemiological association between milk consumption and acne, particularly skimmed. The researchers hypothesize that the association may be caused by hormones (such as bovine IGF-I) present in cow milk; but this has not been definitively shown. Seafood, on the other hand, may contain relatively high levels of iodine, but probably not enough to cause an acne outbreak. Still, people who are prone to acne may want to avoid excessive consumption of foods high in iodine. It has also been suggested that there is a link between a diet high in refined sugars and acne. According to this hypothesis, the startling absence of acne in non-westernized societies could be explained by the low glycemic index of these tribes' diets. [2] Further research is necessary to establish whether a reduced consumption of high-glycemic foods (such as soft drinks, sweets, white bread) can significantly alleviate acne, though consumption of high-glycemic foods should in any case be kept to a minimum, for general health reasons.

• Deficient personal hygiene. Acne is not caused by dirt. This misconception probably comes from the fact that acne involves skin infections. In fact the blockages that cause acne occur deep within the narrow follicle channel, where it is impossible to wash them away. These plugs are formed by the cells and sebum created there by the body. The bacteria involved are the same bacteria that are always present on the skin. It is advisable to clean the skin on a regular basis, but doing so will not prevent acne. Anything beyond very gentle cleansing can actually worsen existing lesions and even encourage new ones by damaging or overdrying skin.
  
• Sex. Common myths state that either celibacy or masturbation cause acne and, conversely, that sexual intercourse can cure it. There is no scientific evidence suggesting that any of these are factual. It is true, however, that sexual activity, as well as anger and stress, affect hormone levels and thus bodily oil production, which can cause acne.