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.
The death of the flea marks the beginning of substage 4b (around day 25 post-penetration) as the body begins to eliminate the parasite through skin repair mechanisms (e.g. shedding and subsequent skin repair). At this phase, the lesion is seen as brown or black.By the 5th stage of tungiasis, the carcass of the T. penetrans flea has been expelled and there are circular skin residues of the infection that remain. There are only lingering symptoms at this time, described in the next section. Morphology
In a study of 1000 freshly ejected T. penetrans eggs, it was found that females are generally smaller than males for all criteria. In some cases, though, females had a bigger epipharynx and maxillar palpus. Due to its burrowing activity, the chigoe flea has developed a well-developed lacinia and epipharynx that is used to penetrate the skin. Overall, the fleas’ head is relatively flattened, which again aids in burrowing through the epidermal and dermal layers.Investigators have also found that adult T. penetrans have different morphologies with respect to the shape of their head. Some have a rounded head, others have head shapes that resemble ski ramps more than anything else; still, others demonstrate head shapes that are very linear with a slight bulge at the nose. These morphologies were seen to be host-specific, as only fleas of some head-types were found in specific hosts.