Patch Testing: RIPT, 48-Hour, or Cumulative?

RIPT vs. 48-hour vs. Cumulative Patch Testing: How do I choose?

Unexpected skin reactions influence user perceptions of your product. In turn, these reactions can significantly influence your brand success and your liability risk. To ensure product success, any product that will contact human skin should be evaluated for both irritation and sensitization well ahead of its introduction to the marketplace. To choose between RIPT vs. 48-hour vs. Cumulative patch testing, it’s important to know the difference between irritation and sensitization.

Skin irritation is an inflammatory reaction that occurs on the skin’s surface at the site of exposure. The irritation affects epidermal cells and is temporary. The irritation is caused by the product, which is likely to produce similar reactions in most individuals. Irritation usually presents as redness and dryness at the exposure site.

Skin sensitization, in contrast, is the result of an internal immune process that causes the skin to display an allergic reaction to a substance after repeat exposure. Instead of being caused by the product itself, the reaction is caused by the body’s immune system. Sensitization in one person does not predict sensitization in others. Sensitization usually presents as an itchy, puffy rash that is not necessarily limited to the exposure site.

What is Patch Testing?

Patch testing is a standard approach to evaluating a product for irritation and sensitization. There are three primary types of patch tests: RIPT vs. 48-hour vs. Cumulative patch testing. CPT℠ has standard protocols for each, and our professional team can develop a custom trial protocol to meet your unique testing needs. In simplest terms, all three methods involve the application of a patch containing a small amount of the test product to a panelist’s skin, leaving it in place for a period of time, and observing the result when the patch is removed.

In practice, a reliable trial involves 25 to 200 panelists (a given percentage of which may have self-identified “sensitive skin”) in a blind evaluation of how skin reacts to the test product in varying concentrations, along with other “control” substances. Evaluation is conducted by highly trained expert evaluators on an exacting timetable, which varies according to the type of trial. When the trial is complete, CPT℠ employs sophisticated analysis to interpret results and deliver a clear, accurate, and useful report of trial findings for you.

48-Hour Patch Test

The 48-hour Patch Test, also known as the Primary Irritation Test, is a simple trial to assess a product’s likelihood of causing irritation. Patches containing the test product in varying concentrations are applied to the panelist’s skin. The patches remain on the skin for 48 hours (2 days), and then the panelist returns to the testing site for patch removal. After patch removal, the site is evaluated immediately and 2 days later for redness, dryness, and other indicators of irritation.

The goal of the 48-hour Patch Test is simple: to determine whether the product will induce irritation.

The Cumulative Irritation Test

The Cumulative Irritation Test (CIT) is a longer trial to measure irritation response to a test product – and changes in that response – over time. Patches of the product are applied to the skin and then are replaced daily (except weekend days) through the course of the trial, usually five, 14, or 21 days. Evaluators observe, grade, and record any signs of irritation daily during the trial period. A final reading is taken the last day of patch removal. The goal of the CIT is to quantitate the irritation potential of the product.

An additional “challenge” phase can be conducted after the CIT, usually two to three weeks after completion. In this challenge phase, the product is introduced to a previously untested site to determine whether sensitization has occurred. The goal of this phase is to evaluate the potential for sensitization.

The Repeated-Insult Patch Test (RIPT)

The Repeated-Insult Patch Test (RIPT) is a two-phase process that is designed to evaluate the sensitization potential of a product. Phase 1 is the induction phase, during which the subject’s skin is exposed to the product several times, usually nine to ten times.

After completion of Phase 1, subjects are given a two-week “rest period.” In any subject who will become sensitized to the product, the immune system will use this time to create the specialized proteins in the body that would bring about an allergic reaction upon subsequent exposures.

In Phase 2, the elicitation phase, the product is reapplied to a new site on the subject’s skin to determine whether the repeat application will elicit an allergic reaction, showing that sensitization has occurred.

Choose a Testing Method that Supports Your Goals with CPT℠ Labs

All three types of patch testing trials have features in common, but each method requires different procedures to meet particular goals. To assist choosing the method best for your particular needs, CPT℠ will first help you to understand what you want to learn from your trial.

To get started, talk to one of our product testing experts to learn more about how to choose a patch testing trial that supports your goals and your bottom line. Contact us at (973) 609-5747.