Since ancient times, humans have combined strange ingredients to create personal care products. Today, the ingredients are only slightly less bizarre. Here are nine weird items you may not have known about.

1. Sodium Chloride (Table Salt)

Good old table salt is a common ingredient in shampoo, facial cleanser, body wash, bubble bath, and anything else that foams. These products are made using specific combinations of surface-active agents (surfactants), which usually require salt to reach a usable viscosity. The next time you shudder with delight while working your hair into a lather, take a second to peek at the back of that shampoo bottle and see if your friend, table salt, is in the mix.

2. Oleoresin Capsicum (Pepper Spray)

If you're a police officer, vigilante, or really serious about self-defense, you know Oleoresin Capsicum is the primary component of pepper spray. Specifically, it's the pepper part. Why, pray tell, would there be pepper spray in your lipstick? Well, there probably wouldn't be (barring the possibility of a horrible, horrible joke), but there might be some capsicum in any product that causes a warming sensation when applied topically (don't think lube—external use only!) and in many over-the-counter pain and itch creams.

3. Diatomaceous Earth (A Component in Dynamite)

Also known as diatomite, this is one of the two components of dynamite (along with nitroglycerin). DE is a silica-based powder made of the fossilized remains of diatoms, a kind of spherical, hard-shelled algae. Because the particles are hollow, they are very porous; it is even utilized in cat litter and water filtration processes. In cosmetics, diatomaceous earth finds a home in natural toothpastes, deodorant, absorbent powders, cuticle cream, and in mild-exfoliation products due to its gentle abrasiveness.

4. Albumen (Egg Whites)

Egg whites are sticky and gooey, but they constrict very efficiently when dried, and are used in skin-firming products for just this reason. Processed for purity and spray-dried for industrial use, albumen doesn't exactly resemble your breakfast. But the next time you take half an hour to use that peppermint hydrating peel-off mask, think about the eggs you left in that pan this morning.

5. Plastics

In addition to the obvious packaging role, plastic serves as a film-former in hair gel, hairspray, barrier products, and liquid bandages. Used as polyvinyl alcohol and various other forms, plastics are easily incorporated into many skin and hair care products. Plastic keeps your coif in that perfect Flock of Seagulls swoop, makes your waterproof mascara waterproof, and suspends those little beads in your eye gel. Speaking of beads, tiny polyethylene spheres are frequently used in exfoliating scrubs. The products are generally marketed as "extra gentle," since they are perfectly round and do not damage the skin's surface when used in moderation.

6. Simethicone (Gas Relief Drops)

To all mommies who have lain awake with a fussy baby, this ingredient is better known as gas relief drops (Mylicon is a popular brand.) For cosmetic and industrial purposes, the generic name "˜antifoam' is usually applied. For the same reasons we ingest it, simethicone is used in cosmetics during the manufacturing process to reduce the surface tension of air or gas bubbles, causing them to collect and rise upward. In a baby, this is called "˜burping' and the process is identical in cosmetic manufacturing, although it lacks the distinctive noise and cuteness.

7. Urea (Formerly Extracted From Urine)

As a cosmetic ingredient, urea is a functional skin-softener and humectant, which means it helps to collect and hold moisture in the skin. And thank goodness it isn't extracted from horse urine anymore, because a form of urea (diazolidinyl urea, specifically) is widely used in all manner of cosmetics, household cleansers and hair products as a broad-spectrum antimicrobial and preservative. (These days, urea is made using the WÃ¶hler synthesis.)

8. Propylene Glycol (Not Antifreeze)

Commonly mistaken for its lethal and less human-contact friendly cousin, ethylene glycol (antifreeze), propylene glycol gets a bad rap. Used to moisturize the skin and hair, as a primary ingredient in "self-warming" products (this time, think lube), and to extract herbal ingredients for greater stability and efficacy than water, propylene glycol is a multi-tasker in the cosmetic quiver of tricks. While it is not toxic or harmful, propylene glycol just so happens to share a few of its unsavory relative's anti-freezing effects; it is commonly used on the wings of aircraft to prevent the accumulation of ice crystals and excess moisture, which can cause drag and erratic flap control.

9. Hydrogenated Vegetable Oil (Or, As My Granny Called It, Shortnin')

This is the exact thing that you buy in the giant metal can, and that comes in a 20-pound brick for the food service industry. Topically, hydrogenated vegetable oil is an amazing skin-softener, emollient, and barrier ingredient. You can find it in most heavy body and foot creams, lip balms, and in some suntan products. Although the trans fat content is a legitimate reason to avoid eating it, it actually improves the cosmetic performance of the ingredient—many substitutions for petrolatum contain a hefty proportion of hydrogenated vegetable oil.

Although some of these ingredients seem out of place, the truth is that they're pretty tame compared to the bugs and such in our ancestors' makeup. (More on that next time.) So, what's the weirdest thing you've noticed in one of your products?