Today we are having a bit of fun with some famously stinky ingredients 😂  Whether or not you find the smell of an ingredient to be pleasant or unpleasant (or worth a bit of unpleasant-ness for its otherwise awesome-ness) is a highly personal thing, so please keep that in mind while I poke a bit of fun at some none-too-pleasantly-perfumed ingredients 😊 I’m not trying to throw a stink bomb into anybody’s ingredient loves! If you adore any of these stinky ingredients, by all means, carry on 😄

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This post was partly inspired by my patron Zil (thank you!) and partly by a lot of “I made X and it smells bad—why?” queries from readers and viewers around the world. I thought we could take a humorous look at a few legendarily smelly ingredients (and what can be done about ’em!), but also chat a wee bit about stinky-ness in general.

First things first: smell your ingredients. If something makes you wretch right out of the bag or bottle, it won’t improve in a formulation. It’ll just end up like those lavender scented dog poop bags—the dog poop still smells like poop… but poop with added lavender. It’s not better, it’s just a slightly different kind of gross. If something smells horrible, please don’t charge ahead making a giant batch of something with it. Different people have different opinions about what smells awful, and different batches of ingredients can smell very different, so the only way to know for sure if your nose doesn’t like something in particular is to smell it yourself.

Up next: always make a wee batch of something before you scale up. In the case of a potentially ruinously stanky ingredient, this gives you a small-scale opportunity to see if the smell comes through in the finished product.

And to segue into the list—watch out for these five famous stinkers!

I got rid of my neem ages ago, and this is the only photo I’ve found that shows it. The neem is the blobs of greeny-brown stuff on top.

Neem oil

Starting with the most legendary of the stanky-pants ingredients seems fitting: Neem oil. This viscous, greenish-brown liquid can be charitably described as smelling like barbeque sauce with distinct notes of molasses, raw garlic, and old cabbage. I have shared two formulations using this fetidly fragrant carrier oil, which is twice as many as I remembered when I sat down to start writing this. I generally used it around 2% and I quickly decided life was too short for neem oil. I threw mine out before a move a few years ago and have never, ever regretted it.

Even people who cheerfully use neem oil admit it smells awful. It is reputed to have some lovely benefits (insecticide, anti-fungal, anti-viral, anti-bacterial), but I just cannot get past the smell. Barb over at Scrub me Down loves herself some neem oil and has an entire “Stinks like A**” formulation series that uses it—definitely check it out if you love yourself some neem!

I’ll wrap up this section with some choice hilarious comments from my reader Suki on her experiences with neem oil:

“I bought a full pint of Neem Oil! It really does smell like butt! & not clean, fresh butt(??), but like old, dirty rancid butt!… If you had neem oil coating your tresses, it’d be like, ‘Gee, Suki, I really thought I liked you,’til I smelled your ol’ rancid dirt-butt head..let’s just correspond online, m’kay?’” – Suki


Oh, lanolin. You are oh-so-lovely for the skin… but you smell like an unwanted hug from a wet, dirty sheep that’s been hanging out by a trash fire. You’re so rich and wonderful in lip products, but dangit, I don’t want to have to hold my breath every time I use my lip balm.

Thankfully, there’s a solution! Refined lanolin (USA / Canada) is more expensive than its greasy sheep-scented predecessor, but the cost is well worth it. I use Lansinoh (thanks for telling me about it, Zil!) and I pick it up at the drug store.

Cupuaçu butter

I think this ingredient might be my neem—the stinky ingredient that I love and will use despite the smell. It’s kind of like chocolate and sour milk, and unfortunately it’s the sour tang that really lifts off the skin and drifts up to your nostrils when it is used in formulations. I adore this silky, moisturizing butter for its silicone-y skin feel, but there’s no denying that unrefined cupuaçu butter smells like someone added bad vinaigrette to your hot cocoa.

This is another instance where refining comes to the rescue! Refined cupuaçu butter doesn’t smell like anything, and for that we can all be grateful 😂

Hydrolyzed silk (sometimes!)

This gorgeous ingredient is a bit of an olfactory gamble. Mine is from New Directions Aromatics and it just smells slightly sweet, but I’ve heard from many readers that their hydrolyzed silk is weapons-grade foul in the scent department, which is obviously a huge bummer. In a case like this I’d recommend looking at any reviews on the supplier website, and perhaps reaching out to the seller to enquire as to the potential putrid-ness of the ingredient. I think it’s utterly lovely, and if you can get a version that doesn’t smell so bad that it ruins your formulations I think you’ll love it 🙈

Learn more about different production methods for hydrolyzing and how they can result in differently scented hydrolyzed silk here.

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(Some) Cationic ingredients

Mmmm…. fish that was forgotten in the microwave. Some sort of a fishy scent is a distinct possibility with cationic ingredients, but I’ve found just how much a cationic ingredient smells like a tuna sandwich abandoned on a radiator can vary massively with the source/batch of an ingredient, and the specific ingredient itself. I’ve had batches of BTMS-50 and BTMS-25 that have just a faint whiff of fish, and some that are much stronger. I’ve only ever had one bag of behentrimonium chloride (BTMC), and hooooooo-eeeeeey that’s a “just 1%” ingredient based on the smell alone. My honeyquat experiences have been pretty putrid, but other readers have reported that their bottles are perfectly lovely. My polyquaternium 7 and cetrimonium chloride barely smell like anything, while my polyquaternium-10 and cationic guar gum have distinctly low-tide vibes. The usage rates of these ingredients are usually low enough that the scents don’t blast through to the finished product, but if you open a new bag of BTMS-50 and feel like you were walloped with a month-old dead whale you might want to make a very wee batch of whatever it is you’re making with it to ensure the scent doesn’t ruin your product.

Bonus Stink

Rancid oils

If an oil has oxidized (gone rancid), it’ll smell distinctly “off”—like crayons, or those very old nuts you found at the back of the pantry that might’ve been left behind by the last tenants (is that an expiry date that starts with “19”?!). This rancid stink will carry through to your final product. Please compost any rancid oils. Yuck.