INCI: Citric Acid
Citric acid is probably one of the go-to ingredients to use as a ph buffer. It is used to lower the ph of anything you’re making or anything you’ve made. High quality citric acid normally comes from the fermentation of citrus fruit sugars which means, of course, it has highly astringent qualities.
It actually not only has ph lowering and preservative qualities, but is also used as an antioxidant.
Some people use citric acid+water in place of aloe vera juice/gel to lower the ph and decrease the chance of bacterial growth in concoctions. It is, though, one of the more irritating AHAs. It is not recommended to use citric acid to exfoliate!
NOTE: Products with a lower ph (around 5 or 4.5) help with closing the hair cuticle. It is recommended, though, to use lactic acid (sodium lactate) instead to lower ph because it is milder than citric acid and offers additional benefits.
I rarely use citric acid for any other reason than to lower the ph and help preserve a concoction. It only takes a really small amount to do its thing. Some people use as little as 1/4 tsp (teaspoon) to help preserve about 16oz (ounces) of lotion.
You’ll also find potassium sorbate (sorbic acid) used along with citric acid to help keep a concoction from going bad before all of it is used.
Since I tend to use my concoctions made with Neodefend (like lotions) within 2 to 3 months, I’ve never had to figure out just how many months (or years) a concoction would last with just citric acid.
Honestly, as long as it isn’t irritating to your skin, something is always better than nothing. Even some tea starts to turn bad in about 3 days of sitting in the fridge.
I can never get more than 1 week of flaxseed gel to last in the fridge without some type of preservative, natural or not, to help it.
Citric acid is also combined with sodium bicarbonate (baking soda) to make awesome bath bombs. They’re the things that fizz up and smell great when you throw them in the tub.
NOTE: The citric acid amount should be 1/2 the baking soda amount. IE: 6oz baking soda, 3oz citric acid; or 8oz baking soda, 4oz citric acid; etc.
Since I tend to use citric acid in very small amounts, I have no experience with any irritation on the skin. If you’re worried about that, use an anti-irritant (like allantoin or chamomile/lavender tea) in your concoctions.