October 2026 FDA Warning Letter: TENS Device Becomes Unapproved When Marketed for Menstrual Cramps, Six Quality Procedures Missing

October 2026 FDA Warning Letter: TENS Device Becomes Unapproved When Marketed for Menstrual Cramps, Six Quality Procedures Missing

On October 2, 2026, the U.S. Food and Drug Administration (FDA) issued a warning letter (CMS # 731847) to Chirp Innovations, LLC of Lehi, Utah. The letter was published on FDA’s website on October 27, 2026. It concerns the company’s over-the-counter TENS/EMS combination product, Chirp Halo Wireless Muscle Stimulator. The inspection covered the Lehi facility from November 18 to 21, 2025.

The product had a clearance. In 2024, it received 510(k) clearance under K241509 for specific uses: in TENS mode, for temporary relief of pain associated with sore and aching muscles in the shoulder, waist, back, neck, upper and lower extremities, abdomen, and buttocks due to exercise or normal household work activities; and in EMS mode, for stimulation of healthy muscles to improve or facilitate muscle performance. Both cleared uses are tied to muscles and strain.

FDA’s finding turned on another word: menstrual cramps. The warning letter cited statements on the company’s website and marketing materials, including drug-free relief of cramps during period days and prompts for users to use the massage and stretching settings in TENS mode to relieve menstrual cramps. The site also sold a six-pack of patches called Halo Menstrual Relief Pad and included an educational section on menstrual pain. FDA’s reasoning was direct: menstrual cramps arise from involuntary uterine contractions related to the menstrual cycle, whereas the cleared uses refer to voluntary muscle soreness caused by exercise or household work. Promoting the device to the menstrual cramp population constituted a major change in intended use and required a new premarket notification.

The legal characterization is significant. Under section 501(f)(1)(B) of the Federal Food, Drug, and Cosmetic Act, a product lacking an effective PMA or IDE is adulterated. Under section 502(o), introducing a device into commercial distribution without notifying FDA of a major change is misbranding. The product had a clearance number, but the promotional claims made it a different, unapproved device. Many teams working on home physiotherapy devices do not appreciate this distinction.

The inspection also exposed system-level deficiencies. FDA found under 21 CFR 820.5 that the company had not established a quality system appropriate for its device. Specifically, six categories of documents were missing: management review under 820.20, quality audits under 820.22, design controls under 820.30, purchasing controls under 820.50, corrective and preventive action under 820.100, and complaint files under 820.198. The company submitted eight responses between December 2025 and August 2026; six were prepared by external consultants and the last two by the company itself. FDA deemed all eight responses inadequate. The company said it had established ISO 13485:2016-compliant system documents and completed training for key positions, but it never provided FDA with procedures for complaint handling, internal audits, device reporting, CAPA, and return authorization. Training attendance does not equal the existence of procedures.

Another issue was reporting. Under 21 CFR 803.17, the company should have had a written medical device reporting procedure to determine whether complaints met reporting thresholds. FDA stated that the company’s vice president of product confirmed that the company had neither an MDR procedure nor an established process for evaluating adverse events. A July 15, 2026 response said the procedure had been approved and put in place, but the text was still not provided, and the company did not state whether it would conduct a retrospective reportability review of existing complaints. Under section 502(t)(2), this constitutes misbranding.

The timing deserves separate attention. The final rule revising Part 820 was issued on February 2, 2024, and the revised Quality Management System Regulation (QMSR) took effect on February 2, 2026. FDA explained that the inspection occurred in November 2025 and applied the Quality System regulation then in force, but the corrective actions proposed by the company must comply with the QMSR effective February 2, 2026. The inspection basis and the remediation basis are two different texts, a detail that is often overlooked.

The consequences appear at the end of the letter: failure to correct may lead to seizure, injunction, and civil penalties; if the violations relate to premarket approval of a Class III device, the application will not be approved until the issues are resolved; and FDA may also refuse to issue a Certificate to Foreign Government (CFG). For export-oriented companies, the last point often affects orders more directly than a monetary penalty.

AIMEILI Regulatory Interpretation

This warning letter is a clear reminder that a 510(k) clearance is tied to a defined intended use, and that marketing claims can change the regulatory identity of a device. Menstrual cramp relief is not a minor variation of exercise-related muscle soreness. It concerns uterine smooth muscle and a different clinical population, and FDA treats promotion for that use as a major change requiring a new premarket submission. Companies should review websites, product listings, social media, influencer scripts, instruction manuals, and customer service scripts against the cleared indications. A claim matrix that maps each claim to the cleared indication, IFU, and supporting evidence is a practical control.

Second, an ISO 13485 certificate or a set of training records does not substitute for FDA-required quality system procedures. FDA expected documented procedures for management review, quality audits, design controls, purchasing controls, CAPA, complaint files, and MDR. The company’s failure to provide the actual procedure texts was central to the warning letter. For global manufacturers, the lesson is to maintain controlled, retrievable, and current FDA-specific procedures, not only ISO-level documentation.

Third, MDR procedures need to be operational, not merely approved. They should define how complaints are evaluated for reportability, who makes the decision, how decisions are documented, and whether retrospective review is needed when a procedure is newly implemented. The absence of a written MDR procedure and the failure to explain retrospective review were separately cited as misbranding.

Fourth, the QMSR transition creates a dual-standard remediation risk. An inspection may be conducted under the older QS regulation, but corrective actions must be designed to meet the QMSR. Companies inspected in the transition period should confirm that remediation plans address QMSR requirements, including risk management and documented processes, rather than only closing the historical observation.

Business Impact

A public warning letter affects more than regulatory status. It can trigger retailer and distributor holds, increase due diligence scrutiny in tenders and supply agreements, and delay or block export certificates. For manufacturers, distributors, CROs, and regulatory affairs teams, the practical priorities are to audit promotional content against cleared intended use, verify that FDA-specific quality procedures are complete and retrievable, and confirm that complaint and MDR workflows include reportability assessment and documentation. Export-focused firms should also assess CFG exposure, because a refusal to issue a CFG can directly interrupt international orders even before any seizure or civil penalty action.

Sources

• U.S. Food and Drug Administration (FDA) — Warning Letter CMS # 731847, Chirp Innovations, LLC, issued October 2, 2026, published October 27, 2026: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/chirp-innovations-llc-731847-10022026
• U.S. Food and Drug Administration (FDA) — Warning Letters: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/compliance-actions-and-activities/warning-letters

This article interprets public regulatory enforcement information and does not constitute a conclusion or commitment regarding any specific product, company, or registration application. Whether a similar product needs a new premarket submission depends on its actual intended use, labeling, instructions, and overall marketing presentation; the official text and subsequent review opinions control.