In adult incontinence testing, an “insult” is one dose of simulated urine applied to a product. A single-insult test applies one dose and measures what happens next. A multi-insult test applies several doses at set intervals and shows whether the product still performs after it is partly wet. The difference matters because a brief that handles the first void well can behave very differently on the second or third, and overnight or bedridden wearers often void more than once between changes. This article explains what each test shows, where each one misleads, which one to request for different product tiers, and how to write the requirement into an RFQ so supplier data can be compared fairly.
Single-insult testing applies one controlled dose of test liquid, usually 0.9% saline, and measures a result such as acquisition time, rewet, or retention. Multi-insult testing repeats the dose, so it measures how the same product performs when the core is already partly loaded. The first approach tests the product at its best. The second is closer to how a care shift actually experiences it.
| Factor | Single-insult test | Multi-insult test |
|---|---|---|
| What it simulates | First void into a dry core | Repeated voids between changes |
| Typical outputs | Acquisition time, rewet, retention or capacity after one dose | Acquisition time per dose, rewet after the final dose, leakage before saturation |
| Main strength | Fast, repeatable, easy to compare across SKUs and batches | Exposes slowdown, gel blocking, and surface return after the core is loaded |
| Main weakness | Cannot show how the core behaves once the SAP has swollen | More variables to control; results depend heavily on dose volume and interval |
| Best use | Incoming QC, batch release, first-round supplier screening | Design validation, overnight and heavy-absorbency SKUs, tender files |
| Cost and lead time | Generally lower | Generally higher, because each sample takes longer to run |
The last row is a general expectation, not a quoted price. Ask the testing lab for actual fees and turnaround.
Single-insult methods are the backbone of most procurement specifications. They are standardized, relatively low-cost, and repeatable.
Three measurements dominate:
Absorbent Product Services’ testing page
, ISO 11948-1 measures the maximum absorption capacity of the whole urine-absorbing aid by weighing it dry, soaking it, draining it, and weighing it wet.
Procurement bodies already build specifications on these numbers. California’s Medi-Cal program, in its incontinence product review and contracting procedures, sets target values for rate of acquisition, rewet, and retention capacity for briefs and protective underwear. It requires results from an independent laboratory and asks for tests on medium and large sizes. That is a useful model for buyers: name the method, name the parameter, and require independent data.
The limit is the word “first.” A single dose lands on a dry acquisition layer and unswollen superabsorbent polymer (SAP). Nothing in the result tells you what the same area does after it has already handled fluid. A product can post a good single-insult rewet number and still struggle later in the night.
Repeated dosing stresses the parts of the design that a first dose never touches. In general terms, three things tend to change as insults accumulate:
These are typical tendencies, not guaranteed outcomes. Their size depends on core design, SAP-to-pulp ratio, layer structure, and dose conditions, which is why the test is informative. The dual-core versus single-core performance trade-offs show the same logic from the construction side. After the first void the SAP begins to swell and the structure changes, so repeated-dose performance depends on how fluid is distributed, not on core count alone.
Published test frameworks already recognize the gap. A recent peer-reviewed Polymers study of commercial absorbent hygiene products noted that its moisture-management measurements simulated single doses while users often experience multiple voiding episodes. It suggested future work should use repeated strike-through time (NWSP 070.7.R2) together with wetback measurement (NWSP 070.8.R1). The methods exist. The practical task for a buyer is confirming which one a supplier’s report actually used.
Thickness does not solve this. A bulkier core can still pool fluid early and feel wet at the surface, which is the point behind why thicker adult diapers are not always better. Multi-insult data is one of the few objective ways to show that difference without relying on how the sample feels in the hand.
The common assumption is that more doses always mean a more realistic test. That holds only when the protocol matches the product and the user.
A multi-insult protocol designed for heavy, bedridden use can punish a light pull-up that was never meant to take repeated voids, and the result will say little about its real market. EDANA makes a related point about its Absorption Before Leakage method. In its ABL test method guidance, EDANA says the method was developed for moderate and severe incontinence products used by bedridden patients. It also says results for out-of-scope products are meaningless because of high variability. The lesson applies to any test: scope decides whether the number means anything.
There is also a cost-and-timing argument for keeping single-insult tests. They suit batch release because they are quick and easy to repeat on every shipment. Multi-insult tests earn their cost during development and qualification.
A practical rule for most programs:
Lightweight redesigns raise the stakes. A supplier may remove pulp to shrink carton volume, as discussed in the analysis of thinner adult diapers and shipping emissions. In that case, repeated-dose data is the evidence that the smaller product still performs after the second void.
Two reports labelled “multi-insult” can be impossible to compare. These are the variables to check, and what to ask about each.
Fewer doses with long gaps give the core time to redistribute fluid. More doses with short gaps leave less time for the SAP and distribution layer to recover. Ask for the dose count and the time between doses. Confirm that every candidate supplier was tested the same way.
A dose volume that suits a heavy brief can swamp a moderate one. Dosing position also matters, because the loading zone differs between products and between users. Ask for the volume per insult and the position used, and whether it matches your target user.
Rewet depends on the pressure applied and on which dose precedes the measurement. The Polymers paper describes its rewet step as placing dry filter paper under a defined weight, with a stated wait before weighing. A report that gives only a rewet figure, with no dose count, load, or timing, cannot be reproduced.
The Medi-Cal document describes rewet as a measure of a product’s ability to withstand multiple incontinence episodes between changes, while naming NWSP 070.9.R1 as the method. In the sections reviewed for this article, it did not spell out dose counts. Tender language and test protocol can drift apart. Confirm the actual protocol in the lab report, not just the label on the spec sheet.
Test every size you intend to sell, or at least the sizes that bracket the range. The Medi-Cal procedure itself asks for medium and large results. Ask whether the sample was a production unit or a hand-built prototype, and whether the lab is independent of the factory.
The table below is a recommendation framework, not a regulatory standard. Adjust it to your market and any tender rules.
| Product or use case | Minimum request | Add multi-insult data when |
|---|---|---|
| Light or moderate pull-up for mobile users | Single-insult acquisition and rewet, plus fit and leakage checks | You are launching a premium “extra protection” claim |
| Standard tab-style brief for daytime care | Single-insult acquisition, rewet, and retention per size | Facilities report wetness at the second change or complaints on repeat voids |
| Heavy or overnight brief | Single-insult baseline, plus multi-insult acquisition and rewet | Always, because wear time spans several voids |
| Institutional, hospital, or tender supply | Independent-lab report per SKU and size, with named methods | Always for heavy tiers; also after any material change |
| Lightweighted or thinner redesign | Side-by-side comparison against the current product | Always, before the lighter version replaces the old one |
A quick desk check can also help before you pay for lab work. The wholesale selection checklist for absorbency, core, and leak guards describes a simple pour-and-press test with tissue under a flat weight. Treat that as a rough screen of surface dryness on samples. It cannot replace a controlled method with defined dose, interval, and load.
Most disputes start with a report that looks complete but leaves out the conditions. Watch for these gaps:
This is a hypothetical scenario, not a customer case. A care-home group compares Sample A and Sample B for night use. After one dose, both show a similar, acceptable rewet. After three doses at set intervals, Sample A shows longer acquisition on the third dose and visibly more surface wetness, while Sample B stays closer to its first-dose behavior. On a single-insult sheet they look equal. On the repeated-dose sheet, they are not. Whether Sample B is worth any price premium depends on cost-in-use: change frequency, linen changes, skin complaints, and staff time. The single-insult report alone could not have separated them.
Put the test conditions into the RFQ so every supplier quotes against the same standard. A workable checklist:
Suppliers should be able to share documents for these items on request. For example, LOVINHUG’s adult diaper test reports and certifications page describes per-SKU test reports covering absorption, rewet, leakage, and breathability. Ask which of those reports use multiple doses, and what dose conditions applied, before relying on the headline numbers.
An insult is a single controlled dose of simulated urine, usually 0.9% saline, applied to an absorbent product during testing. Test protocols define the dose volume, location, and the timing between insults when more than one dose is used.
Neither is better in every case. Single-insult tests suit screening and batch release because they are fast and repeatable. Multi-insult tests suit heavy, overnight, and institutional products, where repeated voids between changes can reveal slower acquisition and higher rewet.
Once the target zone is partly loaded, fluid has less open core area to move into, so more of it sits near the topsheet. Pressure from sitting or lying can then push it back toward the skin. The effect varies with core design.
NWSP 070.9.R1 covers rate of acquisition and rewet for adult incontinence products. NWSP 070.7.R2 and 070.8.R1 cover repeated strike-through time and wetback after repeated strike-through. ISO 11948-1 measures whole-product capacity. Confirm current revisions with the testing lab.
Only if dose count, volume, interval, load, liquid, and sample size match. Different protocols produce different numbers. Request the full test conditions and, where possible, have all candidate samples tested by the same independent lab under the same method.
Not necessarily. Prioritize heavy, overnight, and institutional SKUs, lightweight redesigns, and any product after a material change. Light products for mobile users usually need multi-insult data only when making premium protection claims.
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