Fragrancing salt-based bath products

Hi everyone, I'm hoping to get an expert's opinion on the safety of scenting salt-based bath products (bath salts, bath bombs, etc.) with oil-based fragrances.

The way I understand it, the salts must also contain either enough carrier oil to dilute the fragrance to IFRA recommended level, or enough solubilizer/surfactant to disperse the fragrance into the bath water in order to be safe. Otherwise, once the salts dissolve, you have a slick of pure fragrance oil sitting on top of the bath water.

Introduction to Cosmetic Formulation and Technology (2015) makes a passing reference to the fact that "bath beads and bath salts... are made of water-soluble ingredients...." Would that imply that in mass production, they are scented with water-soluble fragrances altogether avoiding this issue?

Thanks so much for your thoughts on this!



  • Yes there are, hydrosols. A byproduct of the manufacture of absolutes I think. 
  • Thanks, I'm familiar with hydrosols and other water soluble fragrances, but what I'm wondering is if it is obligatory to use those instead of oil-based fragrances when scenting an unsolubilized, oil-free bath salt or bomb.
  • Another kind of vague reference from a textbook (Poucher's Perfumes, Cosmetics, and Soap, 10th Ed., 2000): "Normally, about 0.5-1.0% of perfume is added to the crystals, but all perfumes should be diluted before they are added. ...It should be borne in mind that the solvent is ultimately lost by evaporation, and this adds to the cost of the product. Denatured ethanol or isopropyl alcohol are suitable alcohols to use, but a water-soluble type of perfume can also be employed."

    Emphasis added.
  • I have never done this before, but my guess is that hydrosol is useless, mainly because it has to be used in high doses. 

    I doubt alcohol would be useful for other thing than dispersing the oil on the salt. Just consider this: you have 1% oil in 1kg of salt. Lets say you use 100gr, that's 1gr in at least 100lt that will fill up a tub. Considering you are dispersing the salt and moving constantly it would take a long time for the oil to come together. 

    Anhydrous may be a third option. Would be easier to add an emulsifier.
  • Yes, the fact that there is so little fragrance that it is probably unlikely to agglomerate is the only reason I can imagine that it might be considered safe to use an unemulsified fragrance oil in this kind of product. Other than the fact that most people also use some kind of surfactant while in the bath, effectively solubilizing the fragrance oil as an unintended consequence.

    Personally, I always include a solubilizer when I make this kind of thing, but another person and I were having a bit of a debate about the issue.

    I'm kind of wondering at this point if it isn't almost an issue of semantics; like sure, it would be technically "unsafe" to use undiluted fragrance, but is unlikely to cause harm in practice due to the small quantities and probable incidental solubilization. The devil is in the details, hahah.
  • The overriding factor is this: if your product wrecks some rich persons Jacuzzi, you'd better have insurance. Or work for Lush.
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Well, yes... I was worrying about it more from a skin safety perspective, but I guess ruining plumbing is another reason not to have free-floating oil in the tub.
  • there is another way to incorporate a fragrance into a powder product: premix it with a very absorbent grade of silica (e.g. Sipernat 22 from Evonik)
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • Yes, modified starches like Natrasorb would work too.

    I guess maybe my question wasn't super clear. I'm just wondering if a product like bath salts with an ingredient list of salts + fragrance (+colour) is safe, since it will leave undiluted fragrance oil floating on top of the bath water, coating the bather as they get in the water.
  • Why don't you ask Lush that question?
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • @Belassi, because I'm not convinced that Lush products are properly formulated, and because I don't necessarily trust a retailer to tell me if their products are garbage... especially considering the profit they make.
  • I'm a scientist (in a field entirely unrelated to cosmetic chemistry... ice and permafrost) who makes soap and lotion and bath bombs for friends and family as a hobby. I guess I just prefer my safety info to come from scientists rather than marketers.
  • It seems like an easy problem to solve. (Unintended pun...)
    Add some solid surfactant to the mixture.
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • I use polysorbate 80 as a solubilizer in my bath bombs and have no problem with it. My question is an attempt to resolve a debate I was having with someone about whether a formula including fragrance oil but without a solubilizer would be safe.
  • I think @DAS has made a great point that even if you didn't use a solubilizer, it's still only a tiny amount of fragrance that you're using and being exposed to. You'd have to do the math.

    In truth, there are a lot of unanswered questions in cosmetic science and in toxicology. Much of the advice you hear is based on empirical data & experience. It hasn't always been scientifically "proven". People often just do things because they've worked in the past.

    Unfortunately, this will not help resolve your debate.
  • @ Perry, thanks for your response. I think "science doesn't have the answer to that yet" is a totally acceptable way to end a debate. :) I really appreciate everyone's input on this!
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