Propylene glycol alginate or PGA is an additive used mainly as a thickening agent in certain types of food. It is made from the kelp plant or from certain kinds of algae, which is processed and transformed into a yellowish, grainy chemical powder. The powder is then added to foods that require thickening. Propylene glycol alginate has been used for many years as a food preservative. Many food manufacturing companies use it in the most common household food items.

There are three primary reasons for using propylene glycol alginate. First, it thickens liquid but it also stabilizes it. For example, the foam in beer can be stabilized by using this chemical as can fruit juices or foamy dairy products. Propylene glycol alginate is also considered an emulsifier, which means that it keeps foods fresher because it acts as a preservative. Finally, certain foods have a tendency to change color or consistency over a period of time and this chemical helps to slow down that process.

Most types of gel-like foods, including yogurt, jellies and jams, ice cream, and salad dressing contain propylene glycol alginate. Certain condiments and chewing gum also contain this chemical. Some kinds of cosmetics used on the skin use this chemical as an ingredient to thicken or preserve a make-up product.

Although it is considered a safe additive, there have been reports of negative side effects. It is thought to cause certain medical conditions or diseases. Whether propylene glycol alginate is ingested or used on the skin as a cosmetic, it can produce stomach upset and nausea. When it is only used cosmetically it can cause allergic reactions that include hair loss, rashes, and eye irritations.

It is unclear if this chemical additive should be used by expectant mothers because it is thought to be a teratogen. This means that it can cause possible birth defects. Other skin-related allergies can occur by using a household cleaner that contains this chemical. Propylene glycol alginate side effects are primarily caused cosmetics that list this chemical as an ingredient.

Because it is easily absorbed into the skin, it is thought that exposure can cause damage to the kidneys as well as the liver. High doses of this chemical can cause seizures in children. Propylene glycol alginate is one of the most commonly used chemical additives.