What Is Diammonium Phosphate?
Diammonium phosphate, also known as diammonium hydrogenorthophosphate, is an inorganic salt formed when two molecules of ammonia react with one molecule of phosphoric acid. The result is a white, water-soluble powder with the chemical formula (NH4)2HPO4. Large-scale production begins with phosphate rock that is processed into phosphoric acid. This acid is carefully neutralized with ammonia, then the solution is cooled and crystallized before being dried and milled into a fine powder suited for cosmetic use.
The ingredient first found widespread application in agriculture as a fertilizer owing to its high nutrient content. Its stable pH and low cost soon attracted formulators in food and personal care who needed a dependable buffering agent. Over time it earned a spot in modern cosmetic labs, particularly in products where precise pH control and protection of packaging components are important.
Today you are most likely to encounter diammonium phosphate in water-based creams, lotions, serums, sheet masks, rinse-off masks, hair conditioners, toothpastes and mouthwashes. It appears in both high-tech anti-aging lines and everyday personal care products because it plays well with a wide range of ingredients and processing conditions.
Diammonium Phosphate’s Cosmetic Benefits/Uses
In a skin or hair care formula diammonium phosphate serves several practical roles that keep the product safe and comfortable to use.
- Anticorrosive: Helps prevent metal parts of packaging and processing equipment from rusting when they are in contact with water-rich formulas, which in turn keeps the product looking and performing its best throughout its shelf life
- Buffering: Stabilizes the pH of the formula so it stays within a skin-friendly range, reducing the chance of irritation and helping sensitive active ingredients remain effective
- Oral Care: In toothpastes and mouthwashes it assists in maintaining an optimal pH for enamel health and can support a fresh, clean feel in the mouth
Who Can Use Diammonium Phosphate
Diammonium phosphate is generally suitable for all skin types including oily, dry, combination and sensitive skin because it has a neutral pH and is used in very low amounts. People with an already compromised or severely dehydrated skin barrier may want to pay attention, as the salt component can feel a little drying in high concentrations, but this is uncommon in finished products.
The ingredient is synthetically produced from mineral sources, so it contains no animal-derived material. That makes it appropriate for vegans and vegetarians.
Topical use is considered low risk for women who are pregnant or breastfeeding since systemic absorption is negligible. This is not medical advice, and anyone who is pregnant or nursing should have a quick chat with a healthcare provider before adding new products to a routine just to be safe.
Diammonium phosphate does not make skin more sensitive to sunlight and there are no known interactions with common sunscreen filters. It also plays well with most other cosmetic ingredients, so you rarely have compatibility issues in layered routines.
Potential Side Effects/Adverse Reactions
Reactions to the topical use of diammonium phosphate differ from person to person. The following points list potential side effects, but they are not expected in the average user when the ingredient is used correctly in a professionally formulated product.
- Mild skin dryness or tightness
- Temporary stinging on freshly shaved, broken or highly irritated skin
- Low-grade redness itching or burning in people who are very sensitive to phosphates
- Rare allergic response such as localized swelling or hives
- Unpleasant taste or slight oral irritation if over-used in mouthwashes or toothpastes
- Eye irritation if the product accidentally gets into the eyes
If you experience any of these effects stop using the product and consult a healthcare professional or dermatologist for guidance.
Comedogenic Rating
Rating: 0/5
Diammonium phosphate is a highly water-soluble inorganic salt that leaves no oily film on the skin and is typically used at very low concentrations. Because it does not sit in pores or create an occlusive layer it has virtually no potential to cause blackheads or breakouts. This makes it suitable for people who are prone to acne or congestion.
Since the ingredient readily dissolves in water it is also easy to rinse away, further reducing any chance of residue-related pore blockage.
Summary
Diammonium phosphate acts as a reliable buffering agent that keeps a product’s pH in the sweet spot for skin comfort, an anticorrosive that protects metal parts of packaging and processing equipment and a supporting ingredient in oral care formulas where it helps maintain a tooth-friendly environment. It does this thanks to its phosphate ions which balance acidity and its ability to form a thin passivating layer on metals, all while staying completely soluble in water.
You will not often see diammonium phosphate promoted on the front of the label; it is more of a behind-the-scenes workhorse than a trending active. Still, its versatility, low cost and ease of use keep it popular in lab benches around the world.
Overall safety is considered very high with minimal risk of irritation or allergies for most users. As with any new cosmetic ingredient it is wise to do a quick patch test the first time you try a product that contains it just to be sure your skin agrees with the formula.