What Exactly Is Aluminum Hydroxide, and What's It Used For?

You see "aluminum hydroxide" on ingredient lists but are unsure what it is. This white powder seems mysterious, appearing in everything from plastics to antacids, causing understandable confusion about its purpose.

Aluminum hydroxide is a compound primarily used as a non-toxic flame retardant in plastics and cables. It’s also widely known as the active ingredient in antacid medications that neutralize stomach acid.

From my perspective at our production plant in Henan, I see this powder every single day. We produce different grades for wildly different industries. One batch might be sent to a company that makes wire coatings, while another, much purer batch goes to a pharmaceutical company through a buyer like Mr. Park in Korea. The end-use defines the product. Understanding what this material is and how it works is key to seeing why it’s so valuable in so many places.

What is aluminium hydroxide used for?

You know aluminum hydroxide has uses, but they seem completely unrelated. How can one white powder stop a fire in a plastic component and also soothe an upset stomach?

The primary uses are as a flame retardant and an antacid. It is also used as a filler in plastics and a flocculant in water treatment, demonstrating its high versatility.

At our factory, we fine-tune the properties of aluminum hydroxide¹, like particle size and purity², to match its intended application. The two main uses rely on the same fundamental chemistry but in very different environments.

The biggest market by volume is flame retardants. When plastic containing aluminum hydroxide is heated by a fire, the compound decomposes. This reaction absorbs a lot of heat and releases water vapor. The water vapor cools the material and displaces oxygen, suffocating the fire. It’s an elegant, halogen-free way to make materials safer. In antacids, its function is simpler: it’s a base that neutralizes stomach acid.

What are the uses of hydroxide?

You see the word "hydroxide" and know it’s a chemical term. But you’re not sure what this specific part of the compound does or why it’s so important for its function.

The "hydroxide" part of the molecule is the functional engine. It is responsible for neutralizing acids and for releasing water when heated, which gives aluminum hydroxide its power as both an antacid and a flame retardant.

Let’s look at the chemical formula: Al(OH)₃. It’s one aluminum atom bonded to three hydroxide (OH) groups. These OH groups are the active component. They are a base, which means they readily react with acids. When you take an antacid³, the OH groups in the aluminum hydroxide react with the hydrochloric acid (HCl) in your stomach. The result is aluminum chloride⁴ and simple water (H₂O), effectively neutralizing the excess acid and raising the pH.

The exact same OH groups are responsible for its flame retardant⁵ properties. When you heat Al(OH)₃ to over 200°C, the chemical bonds break, and it decomposes into aluminum oxide (Al₂O₃) and water (H₂O). Those hydroxide groups literally turn into water vapor. This process, called endothermic decomposition⁶, does two things: it absorbs heat energy from the fire, and the steam it releases smothers the flame. So whether it’s calming a fire in your stomach or a fire in a cable, it’s the hydroxide doing the heavy lifting.

What is Almagel used for?

You see a specific product in the pharmacy called Almagel. You know it contains aluminum, and you wonder specifically what it does and how it differs from other antacids.

Almagel is a brand-name medication used to treat heartburn, gastritis, and stomach ulcers. It works by using aluminum hydroxide and magnesium hydroxide to neutralize excess stomach acid and provide pain relief.

This is a perfect real-world example of how our product ends up helping people. A pharmaceutical buyer like Mr. Park would source our high-purity aluminum hydroxide specifically for medications like this. Almagel is a classic combination therapy. It doesn’t just use aluminum hydroxide; it pairs it with magnesium hydroxide⁷ (Mg(OH)₂), another base. There’s a very clever reason for this.

Aluminum hydroxide, when used alone as an antacid, is known to have a potential side effect: constipation. On the other hand, magnesium hydroxide has the opposite potential side effect: a laxative effect. By combining the two in a carefully balanced formula, drug manufacturers can create a product that effectively neutralizes acid while the two main ingredients’ side effects cancel each other out. It’s a smart formulation designed to maximize effectiveness and patient comfort. So, Almagel is used for fast, effective relief from acid-related stomach discomfort.

Is aluminum hydroxide safe for humans?

You hear the word "aluminum" and immediately think of toxicity warnings. This makes you rightly concerned about whether a product like aluminum hydroxide is safe to use in medicine or have in your home.

Yes, when used as intended, aluminum hydroxide is considered very safe for humans. Its chemical form is extremely poorly absorbed by the body, and any tiny amount that is absorbed is easily filtered out by healthy kidneys.

This is the most critical question for any product that comes into contact with people, and it’s something we take seriously as producers. The safety of aluminum hydroxide comes down to one key factor: bioavailability⁸. Bioavailability is how much of a substance actually enters your bloodstream. For aluminum hydroxide, this number is extremely low—well under 1%. Most of it simply does its job in the stomach and then passes right through the digestive system.

The human body is well-equipped to handle the tiny trace amounts that do get absorbed. Healthy kidneys are excellent at filtering aluminum from the blood and excreting it. The only real risk is for individuals with severe, end-stage kidney failure, as their bodies cannot perform this filtering function. For the general population, the safety profile is excellent, which is why it has been approved for use in over-the-counter medications by health authorities like the FDA for decades.

Conclusion

In short, aluminum hydroxide is a highly versatile compound. It’s a critical flame retardant, a common filler, and a safe antacid, with its specific use defined by its manufactured properties.