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 its 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 theyve 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 theres 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.
It is unclear whether eradication of the mite improves acne. Diet
High-glycemic-load diets have been found to have different degrees of effect on acne severity. Multiple randomized controlled trials and nonrandomized studies have found a lower-glycemic-load diet to be effective in reducing acne. There is weak observational evidence suggesting that dairy milk consumption is positively associated with a higher frequency and severity of acne. Milk contains whey protein and hormones such as bovine IGF-1 and precursors of dihydrotestosterone. Studies suggest these components promote the effects of insulin and IGF-1 and thereby increase the production of androgen hormones, sebum, 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.