A hair removal service cannot be performed if which of the following medical conditions is present?

A hair removal service cannot be performed in the presence of scabies because this condition is caused by an infestation of mites, leading to severe itching, inflammation, and potential secondary infections from scratching. Performing hair removal services on skin affected by scabies poses a risk of spreading the infestation to other areas of the skin or to other clients, as well as complicating the client's condition.

In contrast, while crusts, plaques, and nodules may indicate other skin conditions, they do not inherently pose the same level of contagion or risk of spreading an infestation, which is why scabies is highlighted in this context as a condition that necessitates delaying any hair removal treatments until the infestation is fully treated.