is definitionally not flowing." Critics of alternative medicine have spoken out against cupping therapy. Harriet Hall and Mark Crislip have characterized cupping as "pseudoscience nonsense", "a celebrity fad", and "gibberish", and observed that there is no evidence that cupping works any better than a placebo. Pharmacologist David Colquhoun writes that cupping is "laughable... and utterly implausible." Practicing surgeon David Gorski observes that "it's all risk for no benefit. It has no place in modern medicine, or at least shouldn't." Safety In 2016, the Cambodian Ministry of Health warned that cupping could be a health risk and particularly dangerous for people with high blood pressure or heart problems. According to the NCCIH "Cupping can cause side effects such as persistent skin discoloration, scars, burns, and infections, and may worsen eczema or psoriasis". Cupping may cause breaks in the capillaries (small blood vessels) in the papillary dermis layer of the skin, resulting in the appearance of petechiae and purpura. These marks are sometimes mistaken for signs of child abuse when cupping is performed on children. Cupping therapy adverse events can be divided into local and systemic adverse events. The local adverse events may include scar formation, burns, linear bruising or streaks (wet cupping), skin ulcers, undesired darkening of the skin, panniculitis, erythema ab igne, induction of the Koebner phenomenon in susceptible individuals with psoriasis, and pain at the cupping site. A theoretical risk of infection exists but there are no reports of this as of 2012. Claimed uses Cupping practitioners use cupping therapy for a wide array of medical conditions including fevers, pain, poor appetite, indigestion, high blood pressure, acne, atopic dermatitis, psoriasis, anemia, stroke rehabilitation, nasal congestion, infertility, and dysmenorrhea. Claimed mechanism of action Proponents claim cupping has a therapeutic effect and removes unspecified "toxins", stagnant blood, or "vital energy" when used over acupuncture points with the goal of improving blood circulation. Methods Modern suction devices are sometimes used instead of the traditional cups. While details vary between practitioners, societies, and cultures, the practice consists of drawing tissue into a cup placed on the targeted area by creating a partial vacuum – either by the heating and subsequent cooling of the air in the cup, or via a mechanical pump. The cup is usually left in place for somewhere between five and fifteen minutes. Cupping therapy types can be classified using four distinct methods of categorization. The first system of categorization