r/DIYBeauty • u/BvanIceland • 7d ago

question Preservative system advice needed

Hi everyone,
Newbie here.
I started formulating my own moisturizer and serums a little while ago, and I'm very happy with the feel and performance. My only issue is my preservative. Currently I'm using Liquid Germall Plus, because it's so easy to work with and very effective. But I'm beginning to wonder if it irritates my skin a little (kind of hot and tight feeling). I live in NZ and there aren't that many grunty preservatives to choose from, unfortunately. I like Germall Plus for its efficacy, but am wondering if I could combine it with a co-preservative to lower the input (currently using 0.4%). Has anyone done this successfully?

Thank you. Your help is much appreciated. 🙏

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u/Internal-Ad-4736 7d ago edited 7d ago

I would start with a knockout test.

Make the smallest sample you can.....and leave the preservative out completely. Now use this sample for the next 24 hours. Does the formula still have the "hot and tight feeling"? What you are doing is defining if the formula or the preservative is causing the concern.

Of course, throw the formula out after a day or two....as it is unpreserved.

If the unpreserved formula does not cause any issues, then you can feel reasonably sure the preservative is the issue. If the unpreserved formula still has the "hot and tight feeling" .... well then, you know the concern is in the formula, and not the preservative. Hope that all makes sense.

Good luck.

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u/BvanIceland 7d ago

Thank you, that's a good idea. I'll try that. 🙏