Cosmetic Microbio Testing with CRBS Dip Slides

Making sure your cosmetic products are safe for yourself and your customers is extremely important, so in this video I’m going to show you a simple test that you can do at home that can save you time, money and those awkward customer conversations!

This is a collab with who very kindly sent me some products of theirs that I’d been eyeing up for quite some time as I’d wanted to show you these! Let’s open the box together in the video.

CRBS Dip Slides

So, what are CRBS dip slides?  Well, as you’ll be aware as a cosmetic maker (especially in the EU and UK) there are specific lab tests that a cosmetic product has to go through to be considered safe for sale. 

All products need stability testing – see my earlier video on that.

But products containing water also need challenge testing.  Challenge testing involves professional lab testing to test the efficacy of your preservative system, they also test for Microbiological contamination.


  • CRBS Dip-Slides are specifically designed to test for Microbiological Contamination in cosmetic products.
  • Dipslides are made from agar, a jelly-type substance that in its simplest form is food for bacteria, yeasts and moulds. By adding your product to it, you are providing any contamination in your product with food to 'eat'. As the contamination grows, bacteria and yeast will show up as a 'bump' on the agar, and for mould, you will usually see 'fluffy' disk-shaped growth.
  • The Straw coloured agar on CRBS slides is called Tryptone Soya Agar (TSA). TTC (Triphenyl tetrazolium chloride) also known as 'red spot dye' is added to the TSA agar. When bacteria grow on the agar, the addition of the TTC causes this to be visible as red spots (making them much easier to count).
  • The Pink side (Rose Bengal agar) has an antibiotic added to it. This helps prevent bacteria from growing on the Rose Bengal agar. As bacteria grow quicker than yeasts/moulds, without this the bacteria would grow and consume the agar before the yeasts/moulds could. It is also one of the reasons why you should use two swabs per test (to avoid transferring the antibiotic onto the TSA side and in turn causing inaccurate bacterial results).

 CRBS Dip slides

These challenge tests MUST be done if your product contains water, however, they are expensive, and if your product fails the test, you are back to reformulating and paying to test again.

This is where Dip-slides come in.  CRBS Dip slides are an affordable way to pre-test before sending for challenge testing, so that you know your product will pass first time. 

Whilst a challenge and Micobiological test is only done and passed once by the lab, CRBS dip slides also allow you to test each batch before you put it on sale, so that you can be sure that each and every batch of your product is free from any contamination and safe for sale.

Let’s say for example, I made a new hand cream.  It passed stability tests, I then needed to send it for a Challenge test, so I used my CRBS dip slides to ensure it was safe, then sent it to the lab knowing it would pass.  It passes the challenge test first time, I get my CPSR, complete my PIF, upload my product to the cosmetics portal and I’m selling it. 

All the above it done once. 

Then, next time I make a batch, since each batch isn’t challenge tested, I would test that batch to ensure that the same level of safety is achieved.  This keeps a high standard of hygiene when making cosmetics and keeps your customers safe.  It also alerts you to any contamination issues before selling, so that you can track down the cause (whether its an ingredient issues or formulation issue).

Watch the video to see how to use them.

Using CRBS dip slides

To dispose of your dip slides, fill the tube half way (to allow for displacement) with disinfectant/bleach and place the CRBS dip-slide back in for several hours.  It can then be disposed off safely.

I’d recommend these for anyone selling their own cosmetics whether they contain water or not, and also if you buy your products in from overseas. Get a sample and test it this way before committing to a large wholesale order, as its your name on the packaging as the responsible person!

Remember they don’t replace challenge testing, but they definitely help reduce the cost of repeat testing and give you peace of mind that your products are safe for use.

Bacteria on a CRBS Dip Slide

If you want to grab some CRBS dip slides and an incubator then click the link in the description and use code REVEGA at checkout, as have very kindly given a 10% off discount when you use that code.

You have a choice of a few incubators starting with the two-slide option I have which is great for a small business, or you can buy larger ones.  The slides need to be CRBS Dip slides as these are cosmetic testing specific, and note that you will need an incubator for these to give accurate results. Creating a stable heat source for these in your home will not work.

For more information on these slides please do go and have a look at their blog, which I’ve also linked below.  Thanks so much to for sponsoring this video, I’m going to find all of this equipment so useful, I’m sure you’ll spot it in future videos. 

Don’t forget to subscribe and hit the bell so you know when I next upload, and if you want some exclusive formulas, business, regulation and formulation advise then please do checkout my Patreon where you get all of that and one to one messaging for just £4 a month.  Thanks to my existing subscribers and Patrons!

Use discount code REVEGA for 10% OFF your first order

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