What Is Glycerin Used for? Uses, Benefits, and Side Effects

Glycerin is a thick, clear liquid with no fragrance. Glycerin is used in cough syrup, liquid medicines, skin care products, and other products.

Glycerin is a thick, clear liquid with no fragrance. Glycerin benefits extend from medicinal use to cosmetics. It is used as a skin application by itself and added to many cosmetic products. Your doctor may use glycerin as an intravenous injection to treat increased pressure in the brain or eye. Glycerin is made from soybean, palm oil, or coconut oil. It is also derived from animal sources and petroleum. It has many uses in industry, including in the manufacture of explosives, paints, varnishes, inks, textiles, and adhesives.

Glycerin is also known as glycerol and glycerine. It is classified as a sugar alcohol because of its chemical structure but has no intoxicating properties. It is completely miscible with water, ether, and alcohol. It is hygroscopic and absorbs water from its surroundings. 

Glycerin is approved by the Food and Drug Administration as a food additive. It is generally recognized as safe (GRAS) and approved for use in skin care products and other cosmetics. It is the third most common ingredient in cosmetics.

Glycerin is used in various products:

• Cough syrups, to reduce irritation of the throat
• Liquid medicines, to improve smoothness and taste
• Skincare products, to protect skin from any irritants
• Hair conditioner and shaving creams, to bring moisture to the skin surface and keep the skin smooth
• Moisturizers, to keep the skin soft and moist
• Toothpaste, to prevent it from drying
• Food and beverages, to help retain moisture and add bulk, sweetness, and bulk

Glycerol has humectant activity — it draws moisture to the skin's surface. It is useful in the treatment of dry skin. Glycerol-containing moisturizers are effective in eczema, in which the skin is inflamed, dry, and itchy. Glycerol is also an emollient and makes the skin smooth and soft.

Glycerin is frequently used in acne products. About half of such products contain glycerin. Moisturizing the skin is an essential component of acne treatment. Glycerin is the most effective humectant and increases hydration of the outer skin layers (stratum corneum).

Glycerin can give an unpleasant sticky feel if the concentration in the product is too high. Hyaluronic acid and sodium pyrrolidone carboxylic acid (PCA) are also humectants. They can be added to products to reduce the amount of glycerin required.

The stratum corneum may be damaged if your skin is dry or irritated. This leads to significant water loss (trans epidermal water loss, TEWL) and inflammation. Applying glycerine can reverse this condition. Glycerine is often combined with occlusive agents such as petrolatum, lanolin, mineral oil, paraffin, squalene, dimethicone, and cyclomethicone).

Keeping the skin hydrated reduces aging-associated damage and wrinkling. Many anti-aging products contain glycerin, though there is insufficient evidence of efficacy.

Glycerin is used frequently in the cosmetics and skincare industry. It acts as:

• Denaturant
• Humectant
• Skin protectant
• Skin conditioning agent
• Hair conditioner
• Fragrance ingredient

Glycerin is a very safe product for cosmetic use. It is an ingredient in over 15,000 products. It is a versatile ingredient added to bath soaps, lipsticks, skin care products, hair dyes and colors, and suntan preparations. It is safe enough to be included in products used near the eyes and in products meant for babies.

Glycerin is used in medicine in many ways. 

As a laxative. If you have constipation, glycerol draws water into the gut and softens hard stools. This makes them easier to pass.

As enemas and suppositories. Inserted into the rectum, glycerin softens hard stools.

As a diuretic. It acts on the kidneys to increase water and sodium in the urine.

To treat glaucoma. This is a condition of increased pressure in the eye (increased intraocular pressure). Your doctor may prescribe glycerin by mouth. In the bloodstream, it increases osmotic pressure and draws water out of the eye, reducing pressure in the eye.

To treat increased cranial pressure. Increased pressure inside the skull is dangerous for the brain. Glycerine by mouth or intravenous injection can reduce the pressure. This action is valuable before neurosurgery.

If you consume glycerine by itself or as part of a food, it is absorbed from the intestines. Most is converted to fats and triglycerides, but some is used to make glucose or glycogen. Glycerin has no long term side-effects. If taken during pregnancy, it does not cause mutations.

Most of any glycerin you consume is removed by the kidneys in the urine. Almost all of a dose is removed from the body in 2.5 hours.

Glycerin can cause allergic reactions. Most often, it will appear as contact dermatitis. Creams or cosmetics with glycerin cause it, and stopping use reverses the condition. Such allergic reactions to glycerin are rare. One study of moisturizers found burning or itching in only 10% of people using a glycerin product compared to 24% of those using urea-saline cream.

As a food additive, glycerin appears to be safe. It has low acute toxicity. Various studies have shown no genotoxic effects. Glycerin has hygroscopic and osmotic properties and can cause some irritation in the stomach. Long-term experiments did not show cancer-causing effects or other adverse effects. 

Doctors use doses of 1 to 1.5 grams of glycerin per kilogram of body weight in the treatment of glaucoma. Such doses cause nausea, headache, and vomiting in some people. 

You've probably used glycerin for years. It's an ingredient in thousands of cosmetic products of all types. It is also an ingredient in many foods and medicines.

If you want to use glycerin by itself for a specific purpose, read the label carefully. Avoid the high gravity, dynamite, and other grades. Only glycerin marked as USP (United States Pharmacopeia) grade is safe to use on your skin. 

Glycerine suppositories and enemas are available over the counter and are generally safe to use if you have constipation. Don't try to consume glycerin by mouth without your doctor's advice. It can be dangerous.