ZACH Insights / Cupping

The marks are real. The effect is uncertain.

A cup lowers the pressure over the skin, the tissue lifts, blood flow rises and small vessels break. That part is well described. Whether cupping relieves pain more than a convincing imitation does is far less clear. This article separates the two.

By Zacharias Razvi · Updated 14 November 2026 · 9 min read

What cupping is

A cup, a vacuum and the skin.

In dry cupping a glass, plastic or silicone cup is placed on the skin and the air inside is partly removed with a pump, by squeezing the cup or with heat. The lower pressure pulls the skin and the tissue under it up into the cup. The cup can stay in place for a few minutes or be slid over oiled skin. In wet cupping the skin is also scratched or pricked, so that blood is drawn out. This article is about dry cupping.

A review of the physiology by Lowe describes the sequence: the negative pressure stretches skin and underlying tissue and widens the capillaries, blood flow rises, and eventually capillaries rupture so that blood leaks into the tissue. That leak is the round mark that stays for days. 1

General education. The article explains physiology and research. It does not diagnose and it is not individual advice.

Model 1 · Under the cup

What the suction does to the layers of skin.

A section of skin traced from a classic anatomy plate, with a cup on top. Select a step to lower the pressure.

Drawn by ZACH over Gray's Anatomy of the Human Body, 20th edition (1918), Fig. 940, a diagrammatic sectional view of the skin. Layer borders, artery, nerve and Pacinian corpuscle were traced on a 10-pixel grid. The capillary loops in the papillae, the sweat ducts, the fat lobules and the lifting of the tissue are added schematically and are not traced. Not to scale: the plate is magnified, while a real cup is several centimetres wide.

  1. Three layers.

    The epidermis is the outer layer, with a tough surface of dead cells. Below it, the dermis carries blood vessels, nerves and sweat ducts. Its small upward folds, the papillae, hold loops of capillaries close to the surface. Under the dermis lies the subcutaneous tissue, mostly fat, with larger arteries and nerves.

  2. The tissue is lifted.

    When the pressure in the cup falls, the skin and the tissue just under it are drawn up into the cup and stretched. The deeper the tissue, the less it moves. 1

  3. The capillaries widen.

    The stretch widens the capillaries and blood flow in the skin rises. 1 Laser measurements show how large the rise can be. The data after this model gives the numbers.

  4. Small vessels break.

    With enough suction, capillaries rupture and red blood cells leak into the surrounding tissue. Under the skin this is called an ecchymosis, a flat bruise. It is the round mark left by the cup. 1

  5. The body clears it.

    Over the following days, immune cells called macrophages take up the leaked red cells. The enzyme heme oxygenase-1 breaks down the heme in them to biliverdin, bilirubin, iron and carbon monoxide. 1 Biliverdin is green and bilirubin is yellow, which is why a fading mark changes colour.

Measured in volunteers

Blood flow in the skin rises many times over.

Who took part
12 healthy adults in a study by Wang and colleagues. 2
What was compared
Cupping on the back of the upper arm at two levels of suction, −225 and −300 mmHg, each for 5 and 10 minutes, on four different days. Skin blood flow was measured with laser Doppler before and after.
What they found
At its peak after the cup was removed, skin blood flow was 11.1 times the starting value after −225 mmHg and 16.7 times after −300 mmHg.
What it cannot say
Whether the rise in blood flow does anything for pain. The participants had no pain, and the study measured blood flow in the skin only.

Data · Skin blood flow after cupping

Peak blood flow as a multiple of the starting value.

Data: Wang et al., Frontiers in Bioengineering and Biotechnology 2020, 12 healthy adults. Means as reported in the abstract, with spreads of ±2.2 and ±2.6.

Starting value 1. After −225 mmHg: 11.1 times. After −300 mmHg: 16.7 times.

The mark

A bruise, not a sign of toxins.

The round mark is sometimes described as stagnant blood or toxins being drawn out. The physiology does not support that reading. The mark is blood from broken capillaries that now lies in the tissue, and it is cleared in the same way as any other bruise. 1 Its colour depends on how much blood leaked and how far the breakdown has come, not on how much was wrong with the tissue.

Lowe argues that the breakdown products of heme have anti-inflammatory effects in animal and human systems, and suggests this could explain some reported effects of cupping. 1 That is a hypothesis. It has not been shown that these substances, in the amounts released under a cup, change pain in people.

Model 2 · What the comparison changes

Against nothing, cupping looks good. Against a fake cup, it is uncertain.

The same treatment can look effective or not, depending on what it is compared with. Select a comparison.

Data: Wood et al., Journal of Bodywork and Movement Therapies 2020 (neck and low back pain, mostly against no treatment or other care, low-quality evidence); Jenkins et al., JOSPT Open 2026 (against placebo cupping, very low certainty). Mean difference with 95% confidence interval. Scales converted to 0–100 points. Negative values favour cupping.

  1. Compared with doing nothing.

    A review of 21 randomised trials with 1,049 participants found less pain after dry cupping in chronic neck pain, by about 22 points on a 0–100 scale, and in low back pain, by about 19 points. The authors rated the evidence as low quality and called for better trials. 3

    A comparison with no treatment cannot separate the cup from the attention, the expectation and the time spent lying down.

  2. Compared with a convincing fake.

    Placebo cupping uses cups that look and feel similar but apply little or no suction. A 2026 meta-analysis found five such trials with 281 participants. In the short term, the estimate was a 9.9-point reduction, with an interval from a 30.5-point reduction to a 10.7-point increase in pain. 4

    The authors rated the certainty as very low. Four of the five trials had a high risk of bias. The interval includes both a meaningful benefit and a slight harm.

  3. After four weeks and six months.

    One trial reported pain after 4 weeks: 17.2 points lower with real cupping, with an interval from 33.0 to 1.4. One trial reported pain after 6 months: 2.2 points lower, with an interval from 11.8 lower to 7.4 higher. 4 A single trial is too little to rely on.

Why the number of trials is not enough

Many trials, few that can answer the question.

A review from 2025 pooled 72 trials of cupping for pain with 5,720 participants. Most reported benefits, but every one of the 72 trials was judged to have a high risk of bias. 5 Many trials of the same weakness do not add up to strong evidence. The comparison with placebo cupping is the one that tests whether the suction itself matters, and that is where the evidence is thinnest.

What the evidence supports

Cupping raises blood flow in the skin and leaves a bruise that clears over days. Compared with no treatment, people with neck or back pain report less pain afterwards.

What it does not support

That the suction itself relieves pain more than a convincing imitation, that the mark shows toxins or stagnation, or that effects last.

In practice

What to know before a session.

The expected effect on the skin is the round mark, which can be tender like any bruise. The trials in the reviews reported side effects unevenly, so how often less common problems occur is not well known. 3

Because the mark is a bruise, things that make bruising easier matter: medicines that thin the blood, bleeding disorders, fragile or damaged skin, and skin infections or rashes at the site. These belong in the conversation before a session.

A person with pain who chooses cupping because it feels good is making a reasonable choice, as long as it does not replace care that has better evidence. For long-term low back pain, the World Health Organization recommends options such as exercise programmes and education. 7

What this article cannot tell you

The blood-flow study was done in healthy volunteers on the arm. The pain trials are few, small and mostly at high risk of bias, and they cover musculoskeletal complaints only. None of it can say whether cupping will help one person's pain. That needs an assessment.

Sources

Follow the evidence.

  1. Lowe DT. Cupping therapy: an analysis of the effects of suction on skin and the possible influence on human health. Complementary Therapies in Clinical Practice. 2017;29:162–168. PubMed record Supports: stretching of tissue, widening of capillaries, rising blood flow, capillary rupture and ecchymosis, clearance by macrophages and heme oxygenase-1, and the proposed effects of the breakdown products.
  2. Wang X, Zhang X, Elliott J, Liao F, Tao J, Jan YK. Effect of pressures and durations of cupping therapy on skin blood flow responses. Frontiers in Bioengineering and Biotechnology. 2020;8:608509. PubMed record Supports: 12 healthy adults and peak skin blood flow of 11.1 and 16.7 times baseline.
  3. Wood S, Fryer G, Tan LLF, Cleary C. Dry cupping for musculoskeletal pain and range of motion: a systematic review and meta-analysis. Journal of Bodywork and Movement Therapies. 2020;24(4):503–518. PubMed record Supports: 21 trials, 1,049 participants, the estimates for neck and low back pain, the low quality of evidence and the call for better reporting of adverse events.
  4. Jenkins LC, Verhagen AP, Amorim M, et al. The efficacy of dry cupping compared to placebo cupping for people with musculoskeletal complaints: a systematic review with meta-analysis. JOSPT Open. 2026;4(1):23–35. PubMed record Supports: five placebo-controlled trials, 281 participants, all three estimates, the 15-point threshold and the very low certainty.
  5. Yiying W, Shuai D, Bo L, Mei H, Huijuan C. Update evidence of effectiveness on pain relieving of cupping therapy: a systematic review and meta-analysis of randomized controlled trials. Journal of Traditional Chinese Medicine. 2025;45(2):234–253. PubMed record Supports: 72 trials, 5,720 participants and a high risk of bias in all of them.
  6. Gray H. Anatomy of the Human Body. 20th edition, revised by Lewis WH. Philadelphia: Lea and Febiger; 1918. The skin, Fig. 940. Fig. 940 on Wikimedia Commons Supports: the plate traced in Model 1.
  7. World Health Organization. WHO guideline for non-surgical management of chronic primary low back pain in adults in primary and community care settings. 7 December 2023. WHO announcement Supports: exercise programmes and education among the recommended options.

Continue

Where to go from here.

Health Map See pain and recovery among the connected systems. Thirty topics on one interactive map. Next article Pain needs context. Why the same signal can hurt more or less, and how expectation changes it. Newsletter One mechanism at a time. New explanations by email when they are published.

All Insights · How to read evidence · Recovery

General education, not a diagnosis or an individual treatment plan. Models are schematic unless a data source is stated beside the figure. Zacharias Razvi is a final-semester physiotherapy student and is not yet an authorised physiotherapist.