The Claim

Cupping's distinctive circular bruising is often explained to clients as evidence that the suction has drawn stagnant "toxins" up from deep tissue to the surface of the skin, where the body can then eliminate them.

What Negative Pressure Actually Does

A cupping vessel creates a localised area of negative pressure that draws the skin, superficial fascia and underlying soft tissue upward into the cup. This mechanically dilates local capillaries and venules and, at sufficient suction and duration, ruptures some of the smallest and most superficial vessels — producing the same basic process of capillary extravasation and bruising discussed in relation to Gua Sha, just created by suction rather than scraping. The marking that results is, again, localised bleeding and its normal biological clearance, not a toxin extraction process; there is no mechanism by which negative pressure applied to the skin surface could selectively draw specific "toxic" molecules out of deep tissue while leaving the rest of the tissue's contents undisturbed.

What Might Genuinely Be Happening

This does not mean cupping is without plausible physiological effect. The suction produces a measurable local increase in blood flow to the treated area, comparable in principle to the circulatory changes documented with Gua Sha. The sustained negative-pressure stretch applied to skin and superficial fascia may also influence local mechanoreceptor activity and contribute to pain modulation through the same descending inhibitory pathways implicated in other forms of manual therapy. Static and dynamic cupping — where the cup is moved across the skin during treatment — may add a further myofascial gliding component similar in principle to IASTM. None of these plausible mechanisms involve toxin removal.

The Verdict

Verdict

The marking left by cupping is localised capillary bleeding caused by negative pressure, cleared by the same ordinary biological process that resolves any bruise — not evidence of toxins being drawn out through the skin. Any genuine symptomatic benefit is more plausibly explained by increased local circulation, mechanoreceptor stimulation and pain modulation through the nervous system, consistent with the broader evidence base for manual therapy generally.

References & Further Reading

  1. Nielsen A, Knoblauch NT, Dobos GJ, Michalsen A, Kaptchuk TJ. The effect of Gua Sha treatment on the microcirculation of surface tissue: a pilot study in healthy subjects. Explore (NY). 2007;3(5):456-466.
  2. Al-Bedah AMN, Elsubai IS, Qureshi NA, et al. The medical perspective of cupping therapy: effects and mechanisms of action. J Tradit Complement Med. 2019;9(2):90-97.