and promote the formation of comedones. Available evidence does not support a link between eating chocolate or salt and acne severity. Few studies have examined the relationship between obesity and acne. Vitamin B12 may trigger skin outbreaks similar to acne (acneiform eruptions), or worsen existing acne when taken in doses exceeding the recommended daily intake. Stress There are few high-quality studies to demonstrate that stress causes or worsens acne. Despite being controversial, some research indicates that increased acne severity is associated with high stress levels in certain contexts, such as hormonal changes seen in premenstrual syndrome. Other Some individuals experience severe intensification of their acne when they are exposed to hot humid climates; this is due to bacteria and fungus thriving in warm, moist environments. This climate induced acne exacerbation has been termed tropical acne. Mechanical obstruction of skin follicles with helmets or chinstraps can worsen pre-existing acne. However, when acne is caused by mechanical obstruction it is not considered a form of acne vulgaris when being very technical. It would be an other acneiform eruption known as Acne mechanica. Several medications can also worsen pre-existing acne; this condition is the acne medicamentosa form of acne. Examples of such medications include lithium, hydantoin, isoniazid, glucocorticoids, iodides, bromides, and testosterone. When acne medicamentosa is specifically caused by anabolic–androgenic steroids it can simply be referred to as steroid acne. Genetically susceptible individuals can get acne breakouts as a result of polymorphous light eruption; a condition triggered by sunlight and artificial UV light exposure. This form of acne is called Acne aestivalis and it's specifically caused by intense UVA light exposure. Affected individuals usually experience seasonal acne breakouts on their upper arms, shoulder girdle, back, and chest. The breakouts typically occur one-to-three days after they've been exposed to intese UVA radiation. Unlike other forms of acne the condition spares the face; this could possibly be a result of the pathogenesis of polymorphous light eruption, in which areas of the skin that are newly exposed to intense ultraviolet radiation are affected. Since faces are typically left uncovered at all stages of life there's little-to-no likelihood for an eruption to appear there. Studies show that both polymorphous light eruption outbreaks and the acne aestivalis breakout response can be prevented by topical antioxidants combined with the application of a broad spectrum sunscreen. Pathophysiology Acne vulgaris is a chronic skin disease of the pilosebaceous unit and develops