{"id":3677,"date":"2026-04-09T16:37:09","date_gmt":"2026-04-09T13:37:09","guid":{"rendered":"https:\/\/www.elinek.gr\/?p=3677"},"modified":"2026-04-30T13:18:43","modified_gmt":"2026-04-30T10:18:43","slug":"challenge-test-vs-tvc-cosmetics","status":"publish","type":"post","link":"https:\/\/www.elinek.gr\/en\/challenge-test-vs-tvc-cosmetics\/","title":{"rendered":"Challenge Test or TVC? What Cosmetic Brands Need to Know About Microbiological Testing"},"content":{"rendered":"
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Challenge Test or TVC? What Cosmetic Brands Need to Know About Microbiological Testing<\/h2>\n

Two tests. Two different questions. Many brands confuse them \u2014 or commission only one when both are needed. Here is how to tell them apart and use each correctly.<\/p>\n

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When brands come to us at Elinek for microbiological testing, one of the first things we clarify is the distinction between the Preservative Efficacy Test<\/strong> (commonly called the challenge test) and the Total Viable Count<\/strong> (TVC) \u2014 also known as the microbial limit test. These two tests answer fundamentally different questions, and understanding the difference will save you time, money, and compliance headaches.<\/p>\n

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\"ComparisonIn simple terms: the challenge test tells you whether your preservative system can defend<\/em> the product against contamination. The TVC tells you whether the product is already contaminated<\/em> \u2014 or within acceptable microbial limits \u2014 at the time of testing.<\/p>\n

What the challenge test actually involves<\/h2>\n

ISO 11930:2019 defines the standard methodology for preservative efficacy testing of cosmetics. The test uses five reference microorganisms: Pseudomonas aeruginosa<\/em>, Staphylococcus aureus<\/em>, Candida albicans<\/em>, Aspergillus brasiliensis<\/em>, and Escherichia coli<\/em>. Each is introduced into the product at a defined concentration, and viable counts are taken at days 7, 14, and 28.<\/p>\n

Results are evaluated against two sets of criteria:<\/p>\n

\"ISO<\/p>\n

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Important:<\/strong> Products intended for use around the eyes, on broken or damaged skin, on children under three years of age, or on immunocompromised individuals require particular attention.<\/div>\n
For these categories, Criteria A is strongly preferred, and any deviation requires robust scientific justification.<\/div>\n
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When is each test required?<\/h2>\n