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Heat therapy

Pooled trials found heat wraps and pads eased period pain against no treatment and an unheated patch, and matched or slightly exceeded NSAIDs or acetaminophen. A heat wrap eased acute low back pain slightly against an oral placebo. Hot water bottle burns and heating pad rashes are documented harms, with no rates published.

Add to Bio HackChecked 2026-11-13
Status
A practice, not a regulated product. FDA classifies chemical hot or cold disposable packs as class I devices exempt from premarket notification [1], and powered heating pads as class II devices, also exempt [2].
Also called
heat wrap, heat patch, heating pad, heat pack, hot water bottle, warm compress, ThermaCare, adhesive heat patch, superficial heat, thermotherapy
Practiced for
period pain, menstrual cramps, endometriosis pain, low back pain, muscle soreness after exercise, stiff muscles, pelvic pain

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help7

Reported risks2

What people practice it for, and what was found

Shown to help7

StrongStudied in women

Period pain, compared with no treatment

Shown to ease period pain in women against no treatment, by about 1.9 cm on a 10 cm scale over 3 months of use, in pooled trials of low certainty.

Compared with no treatment [3][4]

The numbers and sources
Effect
Across 25 trials (2,393 women), pain after 3 months was lower with heat than with no treatment (WMD -1.85 cm, 95% CI -2.29 to -1.41). Within 24 hours of a painful period, the difference was larger (WMD -3.52 cm, 95% CI -5.01 to -2.02, 3 trials, 248 women) [3]. An earlier review found one trial of 132 women in which heat lowered pain against no treatment (MD -4.04, 95% CI -4.88 to -3.20) [4].
Population
5,359 women with primary dysmenorrhea in 57 trials [3]. 6 trials [4].
Sources
[3], [4]
Caveats
Women knew whether they were using heat, so expectation can add to the effect. The reviewers judged the evidence low in certainty and write that heat "may" reduce pain [3]. The earlier review's comparison rests on one trial [4].
ModerateStudied in women

Period pain, compared with an unheated patch

Shown to ease period pain in women more than an unheated placebo patch, in two trials. Mean pain relief over 2 days was 3.27 with heat against 1.95 without.

Compared with an unheated patch with a placebo pill (sham) [4][5]

The numbers and sources
Effect
Over 2 days, mean pain relief scores were 3.27 with a heated patch and placebo pill, 3.07 with an unheated patch and ibuprofen, 3.55 with both, and 1.95 with an unheated patch and placebo pill (all P ≤ .001 against the sham) [5]. A review found two trials favoring heat over unheated placebo therapy [4].
Population
84 women, 81 completing, in a double-dummy trial [5]. 6 trials [4].
Sources
[5], [4]
Caveats
A heated and an unheated patch feel different, so the blinding may be imperfect. The trials are small.
StrongStudied in women

Period pain, compared with pain medicines

Shown to ease period pain in women as much as, or slightly more than, NSAIDs or acetaminophen, in two reviews of trials.

Compared with NSAIDs [3]; pain medicines [4]; ibuprofen 400 mg three times a day [5]; acetaminophen 1,000 mg [6]

The numbers and sources
Effect
After 3 months, pain was slightly lower with heat than with NSAIDs (WMD -1.10 cm, 95% CI -1.51 to -0.70, 22 trials, 1,938 women), and within 24 hours (WMD -1.50 cm, 95% CI -2.86 to -0.15, 2 trials, 167 women) [3]. Against pain medicines, heating pads lowered pain (SMD -0.72, 95% CI -0.97 to -0.48, 2 trials, 274 women) [4]. Heat with a placebo pill gave mean relief of 3.27 against 3.07 for ibuprofen with an unheated patch. Adding heat to ibuprofen did not raise relief (P = .096) but shortened the time to noticeable relief from 2.79 to 1.5 hours [5]. Against acetaminophen 1,000 mg, a heat wrap gave more relief over 8 hours (2.48 against 2.17, p = 0.015) and less cramping [6].
Population
Women with primary dysmenorrhea in 22 trials [3] and 2 trials [4]. 81 women [5]. 344 women [6].
Sources
[3], [4], [5], [6]
Caveats
The pooled certainty was low [3]. The single-day acetaminophen trial blinded only the investigator [6].
Moderate

Acute low back pain, compared with an oral placebo

Shown to ease acute and subacute low back pain slightly against an oral placebo after 5 days, by about 1 point on a 0 to 5 scale, in two trials.

Compared with oral placebo [7]; a comparison the abstract does not describe, for a heated blanket [7]

The numbers and sources
Effect
In two trials of 258 people, a heat wrap reduced pain after five days against oral placebo (WMD 1.06, 95% CI 0.68 to 1.45, on a 0 to 5 scale). In one trial of 90 people, a heated blanket reduced acute pain immediately after use (WMD -32.20, 95% CI -38.69 to -25.71, on a 0 to 100 scale). There was not enough evidence to judge cold, and conflicting evidence on heat against cold [7].
Population
1,117 people in 9 trials, most with acute or subacute low back pain [7].
Sources
[7]
Caveats
The reviewers call the evidence moderate for a small short-term effect, from few trials. No pooled trial covered chronic low back pain [7].
Limited

Acute low back pain, compared with ibuprofen and acetaminophen

One trial found a heat wrap eased acute low back pain more than ibuprofen 1,200 mg or acetaminophen 4,000 mg a day, on day 1 and days 3 to 4.

Compared with ibuprofen and acetaminophen [8]

The numbers and sources
Effect
Day 1 pain relief averaged 2 with the heat wrap, 1.51 with ibuprofen and 1.32 with acetaminophen. Relief on days 3 to 4 averaged 2.61, 1.68 and 1.95. Trunk flexibility and disability also improved more with heat [8].
Population
371 adults with acute nonspecific low back pain, 113 on heat, 106 on ibuprofen and 113 on acetaminophen [8].
Sources
[8]
Caveats
Only the investigator was blinded, and the placebo and unheated-wrap groups (20 and 19 people) were there for blinding, not for comparison [8].
Limited

Acute low back pain, heat with exercise

One trial found a heat wrap plus exercise restored function in 72% of people with acute low back pain, against about 20% with heat, exercise or a booklet alone.

Compared with an education booklet [9]; exercise alone [9]; a heat wrap alone [9]

The numbers and sources
Effect
Two days after 5 days of treatment, 72% of the heat plus exercise group had returned to pre-injury function, against 20% with heat alone, 20% with exercise alone and 19% with the booklet. Function improved 175% more than with the booklet [9]. A Cochrane review reports the same finding of added benefit from exercise [7].
Population
100 adults, mean age 31, with low back pain of less than 3 months [9].
Sources
[9], [7]
Caveats
One small trial with about 25 people per group [9].
Moderate

Muscle soreness after exercise

Shown to ease muscle soreness after exercise when applied within an hour, in pooled trials, with hot packs ranking highest in a network analysis.

Compared with control groups the abstract does not describe [10]; passive recovery and other cold and heat methods [11]

The numbers and sources
Effect
Heat lowered soreness within 24 hours (SMD -1.17, as reported with a 95% CI of -2.62 to -0.09) and after 24 hours (SMD -0.82, 95% CI -1.38 to -0.26). Hot packs lowered it within 24 hours (SMD -2.31) and after (SMD -1.78), while other heat methods did not differ from control. Heat and cold did not differ from each other (P = 0.16) [10]. In a network analysis of ten methods, hot packs ranked first for pain relief at 24 and 48 hours [11].
Population
1,098 people in 32 trials [10]. 1,367 people in 59 trials [11].
Sources
[10], [11]
Caveats
Both reviews come from the same group and note limited trial quality [10][11].

Claimed, not studied in people1

Untested

Endometriosis pain

Not studied in people. Users report: 70% of 484 Australian women with endometriosis used heat, rating it 6.5 out of 10 for pain relief.

No study in people. This rests on what users report.

The numbers and sources
Effect
In a national online survey, heat was the most common self-management strategy (70%), with a mean self-rated effectiveness for pain of 6.52 on a 10-point scale [12]. A narrative review notes that women with endometriosis frequently use heating devices for period and pelvic pain [13].
Population
484 women aged 18 to 45 in Australia with confirmed endometriosis, recruited through support groups [12].
Sources
[12], [13]
Caveats
A self-selected survey with no comparison group. No trial of heat for endometriosis pain was located.

Protocols studied

Period pain trials used an abdominal heat patch for about 12 hours a day for 2 days [5], a heat wrap over one day [6], or heat over 3 months or within 24 hours of pain [3]. Low back pain trials used a heat wrap at 40°C for 8 hours a day over 2 treatment days [8], or for 5 consecutive days with or without exercise [9], and one used a heated blanket [7]. Muscle soreness trials applied heat within 1 hour after exercise [10].

Risks

Reported risks2

LimitedHow often is not known

Burns from hot water bottles and heating pads

Case series: 85 hot water bottle burns at one UK burns unit over 9 years, 8% needing skin grafts, and 88 at one German center, mostly second-degree and in women.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Of 85 patients, 39 children and 46 adults, most had scalds covering a mean 3.07% of body surface. Seven (8.24%) needed debridement and skin grafts, and healing took a mean 28.87 days. Spontaneous rupture of the bottle caused 48.2% of injuries, spills 33% and direct contact 18.8% [14]. Of 88 patients at a German center from 2014 to 2024, 81.8% had second-degree burns and 81.8% were women, most often on the lower trunk, thighs and forearms. Burns fell 7% for each 1°C rise in outdoor temperature [15].
Population
85 patients at a UK regional burns unit, 2004 to 2013 [14]. 88 patients at a German burns center [15].
Sources
[14], [15]
Caveats
Case series with no count of users, so no rate. Many burns came from bottles used for warmth rather than for pain.
LimitedHow often is not known

Mottled skin rash from long-term heat (erythema ab igne)

Case reports: long-term heating pad use caused erythema ab igne, a mottled brown rash. Rare reports describe skin cancer arising in these patches.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Three patients who used heating pads for 6 months to 3 years developed the rash, which caused no symptoms and is expected to fade after stopping [16]. A review describes the rash in women using heat for endometriosis pain and states that malignant change is supported only by low-level evidence [13]. Another review reports squamous cell carcinoma arising in some long-standing patches [17].
Population
3 patients [16]. Published cases [13][17].
Sources
[16], [13], [17]
Caveats
Case reports give no rate.

Checked, no increase found1

Moderate

Side effects in trials

Not shown to raise side effects in trials. In pooled period pain trials, adverse effects were about 70% less frequent with heat than with NSAIDs.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 8 trials of 728 women, adverse effects were less frequent with heat than with NSAIDs (RR 0.30, 95% CI 0.15 to 0.59) [3]. In a back pain trial, no adverse event was serious, and the highest rate, 10.4%, was in the ibuprofen group [8].
Population
728 women [3]. 371 adults [8].
Sources
[3], [8]
Caveats
The abstracts do not give the rate of skin redness or burns in the heat groups.

Claims tested and not found

  1. That adding heat to ibuprofen gives more period pain relief than ibuprofen alone. Total relief did not differ (P = .096), though relief came sooner with both [5].
  2. That heat eases muscle soreness more than cold. Pooled trials found no difference between heat and cold (P = 0.16) [10].

Related

NSAIDsAcetaminophenTENS

Sources

  1. US Food and Drug Administration. 21 CFR 890.5710, Hot or cold disposable pack. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-890.5710
  2. US Food and Drug Administration. 21 CFR 890.5740, Powered heating pad. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-890.5740
  3. Yuan D, Liu Y, Chen Z, et al. Heat therapy for primary dysmenorrhea: a systematic review and meta-analysis. Frontiers in Medicine. 2026. https://doi.org/10.3389/fmed.2025.1730505
  4. Jo J, Lee SH. Heat therapy for primary dysmenorrhea: A systematic review and meta-analysis of its effects on pain relief and quality of life. Scientific Reports. 2018. https://doi.org/10.1038/s41598-018-34303-z
  5. Akin MD, Weingand KW, Hengehold DA, et al. Continuous low-level topical heat in the treatment of dysmenorrhea. Obstetrics & Gynecology. 2001. https://doi.org/10.1016/s0029-7844(00)01163-7
  6. Akin M, Price W, Rodriguez G, et al. Continuous, low-level, topical heat wrap therapy as compared to acetaminophen for primary dysmenorrhea. The Journal of Reproductive Medicine. 2004. https://pubmed.ncbi.nlm.nih.gov/15493566/
  7. French SD, Cameron M, Walker BF, Reggars JW, Esterman AJ. Superficial heat or cold for low back pain. Cochrane Database of Systematic Reviews. 2006. https://doi.org/10.1002/14651858.cd004750.pub2
  8. Nadler SF, Steiner DJ, Erasala GN, et al. Continuous low-level heat wrap therapy provides more efficacy than ibuprofen and acetaminophen for acute low back pain. Spine. 2002. https://doi.org/10.1097/00007632-200205150-00003
  9. Mayer JM, Ralph L, Look M, et al. Treating acute low back pain with continuous low-level heat wrap therapy and/or exercise: a randomized controlled trial. The Spine Journal. 2005. https://doi.org/10.1016/j.spinee.2005.03.009
  10. Wang Y, Li S, Zhang Y, et al. Heat and cold therapy reduce pain in patients with delayed onset muscle soreness: A systematic review and meta-analysis of 32 randomized controlled trials. Physical Therapy in Sport. 2021. https://doi.org/10.1016/j.ptsp.2021.01.004
  11. Wang Y, Lu H, Li S, et al. Effect of cold and heat therapies on pain relief in patients with delayed onset muscle soreness: A network meta-analysis. Journal of Rehabilitation Medicine. 2022. https://doi.org/10.2340/jrm.v53.331
  12. Armour M, Sinclair J, Chalmers KJ, Smith CA. Self-management strategies amongst Australian women with endometriosis: a national online survey. BMC Complementary and Alternative Medicine. 2019. https://doi.org/10.1186/s12906-019-2431-x
  13. Scurtu F, Scurtu LG, Baușic AIG, Petca A, Mehedințu C. Erythema ab igne, a potential cutaneous marker of chronic heat use in patients with endometriosis: a narrative literature review and a case report. Life. 2025. https://doi.org/10.3390/life15101533
  14. Jabir S, Frew Q, El-Muttardi N, Dziewulski P. Burn injuries resulting from hot water bottle use: a retrospective review of cases presenting to a regional burns unit in the United Kingdom. Plastic Surgery International. 2013. https://doi.org/10.1155/2013/736368
  15. Milewski MR, Schlottmann F, Matthias Enechukwu AO, et al. Hot water bottle burn injuries: a 10-year retrospective analysis of incidence and potential predictors in Germany. Innovative Surgical Sciences. 2026. https://doi.org/10.1515/iss-2024-0042
  16. Aria AB, Chen L, Silapunt S. Erythema ab igne from heating pad use: a report of three clinical cases and a differential diagnosis. Cureus. 2018. https://doi.org/10.7759/cureus.2635
  17. Wilder EG, Frieder JH, Menter MA. Erythema ab igne and malignant transformation to squamous cell carcinoma. Cutis. 2021. https://doi.org/10.12788/cutis.0145

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